UNIVERSITY OF LJUBLJANA FACULTY OF ELECTRICAL ENGINEERING LABORATORY OF SEMICONDUCTOR DEVICES UDK 621,3:(53+54+621 +66)(05)(497.1 )=00 ISSN 0352-9045 INFORMACIJE MIDEM 2 o 2003 INFORMACIJE MIDEM LETNIK 33, ŠT. 2(106), LJUBLJANA, JUNIJ 2003 INFORMACIJE MIDEM VOLUME 33, NO. 2(106), LJUBLJANA, JUNE 2003 Revija izhaja trimesečno (marec, junij, september, december). Izdaja strokovno društvo za mikroelektroniko, elektronske sestavne dele in materiale - MIDEM. Published quarterly (march, june, september, december) by Society for Microelectronics, Electronic Components and Materials - MIDEM. Glavni in odgovorni urednik Editor in Chief Tehnični urednik Executive Editor Dr. IztokŠorli, univ. dipl.ing.fiz. MIKROIKSd.o.o., Ljubljana Dr. Iztok Šorli, univ. dipl.ing.fiz. MIKROIKS d.o.o., Ljubljana Uredniški odbor Editorial Board Časopisni svet International Advisory Board Naslov uredništva Headquarters Prof. dr. Rudi Babič, univ. dipl.ing., Fakulteta za elektrotehniko, računalništvo in informatiko Maribor Dr. Barbara Malič, univ. dipl.ing. kern., Institut Jožef Stefan, Ljubljana Prof. dr. Slavko Amon, univ. dipl.ing. el., Fakulteta za elektrotehniko, Ljubljana Prof. dr. Marko Topič, univ. dipl.ing. el., Fakulteta za elektrotehniko, Ljubljana Prof. dr. Rudi Babič, univ. dipl.ing. el., Fakulteta za elektrotehniko, računalništvo in informatiko Maribor Dr. Marko Hrovat, univ. dipl.ing. kem., Institut Jožef Stefan, Ljubljana Dr. Wolfgang Pribyl, Austria Mikro Systeme Intl. AG, Unterpremstaetten Prof. dr. JanezTrontelj, univ. dipl.ing. el., Fakulteta za elektrotehniko, Ljubljana, PREDSEDNIK - PRESIDENT Prof. dr. CorClaeys, IMEC, Leuven Dr. Jean-Marie Haussonne, EIC-LUSAC, Octeville Darko Belavič, univ. dipl.Ing. el., Institut Jožef Stefan, Ljubljana Prof. dr. Zvonko Fazarinc, univ. dipl.ing., CIS, Stanford University, Stanford Prof. dr. Giorgio Plgnatel, University of Padova Prof. dr. 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Grafična priprava in tisk BIRO M, Ljubljana Printed by Naklada 1000 Izvodov Circulation 1000 issues Poštnina plačana pri pošti 1102 Ljubljana Slovenia Taxe Percue UDK621.3:(53+54+621 +66), ISSN0352-9045 Informacije MIDEM 33(2003)2, Ljubljana ZNANSTVENO STROKOVNI PRISPEVKI PROFESSIONAL SCIENTIFIC PAPERS V.Matko: Senzor poroznosti 73 V.Matko: Porosity Sensor R.Osredkar: Osnove teorije optičnih preslikav, prirejene za potrebe simulacij fotolitografskega procesa 79 R.Osredkar: Basics of Optical Imaging Theory Applied to the Photolithographic Process Simulation M.Verderber, A.Žemva: Strojno in programsko razdeljena optimizacija in FPGA implementacija MPEG-2 video dekoderja 86 M.Verderber, A.Zemva: HW/SW Partitioned Optimization and VLSI-FPGA Implementation of the MPEG-2 Video Decoder B.Kodek: Montaža plošč tiskanih vezij z zlitinami brez svinca 92 B.Kodek: Assembling of Printed Circuits Boards with the Lead Free Alloys L. Knez: Induktivni senzorji 96 L. Knez: Inductive Sensors A.Šoštarič, B.lmperl, B.Jerabek: Hišna avtomatizacija na pohodu 100 A.Sostaric, B.lmperl, B.Jerabek: Home Automation On The Move F.Koplan: ABS-senzorji na osnovi AINiCo-magnetov 105 F.Koplan: ABS Sensor Applications Based on AINiCo Magnets A.PIeteršek: 12-bitni bliskovni DAC 110 A.PIetersek: A 12-bit Flash ADC V. Kune, M. Atanasijevič Kune: Avtomatsko nastavljanje ojačenja v brezkontaktnih komunikacijskih sistemih 115 V. Kunc, M. Atanasijevic Kunc: Automatic Gain Adjustment in Contactless Communication Systems A.Pevec, J.Trontelj: Mikrosistem za merjenje električnega toka 118 A.Pevec, J.Trontelj: Microsystem For Electrical Current Sensing M.Topič: Čestitka prof. dr. Mariji Kosec za priznanje Ambasador Republike Slovenije v znanosti za leto 2003 122 M.Topic: Congratulations to prof.dr.Marija Kosec -Ambassador of Science of the Republic of Slovenia for year 2003 I.Pompe: Posvet o novih tehnologijah 125 I.Pompe: Symposium on New Technologies MIDEM prijavnica 127 MIDEM Registration Form Slika na naslovnici: Front page: VSEBINA CONTENT Obnovitev članstva v strokovnem društvu MIDEM in iz tega izhajajoče ugodnosti in obveznosti Spoštovani, V svojem več desetletij dolgem obstoju in delovanju smo si prizadevali narediti društvo privlačno in koristno vsem članom.Z delovanjem društva ste se srečali tudi vi in se odločili, da se v društvo včlanite. Življenske poti, zaposlitev in strokovno zanimanje pa se z leti spreminjajo, najrazličnejši dogodki, izzivi in odločitve so vas morda usmerili v povsem druga področja in vaš interes za delovanje ali članstvo v društvu se je z leti močno spremenil, morda izginil. 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Članarino lahko plačate na transakcijski račun društva pri A-banki : 051008010631192. Pri nakazilu ne pozabite navesti svojega imena! Upamo, da vas delovanje društva še vedno zanima in da boste članstvo obnovili. Žal pa bomo morali dosedanje člane, ki članstva ne boste obnovili do konca leta 2003, brisati iz seznama članstva. Prijavnice pošljite na naslov: MIDEM pri MIKROIKS Stegne 11 1521 Ljubljana Ljubljana, april 2003 Izvršilni odbor društva UDK621.3:(53+54+621 +66), ISSN0352-9045 Informacije MIDEM 33(2003)2, Ljubljana POROSITY SENSOR Vojko Matko University of Maribor, Faculty of Electrical Engineering and Computer Science, Maribor, Slovenia Key words; porosity, soils, glass test tube, capacitive-dependent crystal, direct digital method. Abstract: In response to a need for a more accurate porosity measuring method for small solid samples (approximately 1 g in mass) the porosity measurement sensor using a sensitive capacitive-dependent crystal was developed. This paper presents the new sensor and the probe sensitivity, frequency dependence on the volume. In addition, the new idea of excitation of the entire sensor with stochastic test signals is described, and the porosity measuring method is provided. The latter includes the influence of test signals on the weighting function uncertainty. The experimental results of the porosity determination in volcanic rock samples are presented. The uncertainty of the porosity measurement is less than 0.1 % in the temperature range 10-30 °C. Senzor poroznosti Ključne besede: poroznost, zemljine, steklena merilna epruveta, kapacitivno odvisni kristali, direktna digitalna metoda. Izvleček: V iskanju bolj natančnega merjenja poroznosti malih trdnih delcev (mase približno 1 g) je bila razvita metoda, ki uporablja kapacitivno odvisne kristale. V delu je prikazan novi senzor in njegova frekvenčna odvisnost od volumna. V nadaljevanju je prikazana nova ideja vzbujanja senzorja s stohastični-mi signali in zmanjšanje merilne negotovosti vpliva sistema (senzorja). Prikazani so eksperimentalni rezultati merjenja poroznosti vulkanskega pepela s pogreškom 0.1% v temperaturnem območju 10 - 30°C. 1 Introduction Porosity is defined as the ratio of the volume of voids to the total volume of the material. Solid rock is often not so solid. Sandstone might have started out as a sand dune or a beach, which got buried and compressed. But spaces and pores, remain between the particles. Soils, too, contain pores, which can be classified as micro and macro. Pore diameters larger than 0.06 mm are called macropores and those less as micropores. Soils may be considered as a porous four-phase system composed of air, water, solids and admixtures. The latter are a mixture of water and solids and are soft. In this four-phase soil system, the density p of soils is defined as the ratio of the sum of mass m to the sum of volume V of various soil phases /1 /-/3/ p = 2X ïr, ms+mw + ma+ma V +V +V +V, Jm.=m +tn +m +m . ^^ i s w a ad, yv.=v+v +v +VA jCmU 1 s w a aâ (1) (2) (3) where s solid phase w water phase a air phase ad admixture. Equation (1 ) can also be rewritten as pV+pV+pV+p ,V , ^ _ r s s "w w r g g i ad ad V +v +v +v. s w a aa where solid particle density is m p = — s water phase density is m P» = — K ' air phase density is m V ' a and soil admixture density is m., Pad = v. (4) (5) (6) (7) (8) Instead of density, the specific gravity can be written. From equation (4) we can write (pz + px + pz + p m-g v + v + v + v, ' (9> s w a ad In practice, we can define mass as the ratio of weight of soil to gravity W (10) m = ■ S 73 Informacije MIDEM 33(2003)2, str. 73-78 V. Matko: Porosity Sensor During weighting in air the mass must be increased due to the presence of the air (Avogadro's law) W m = — + p -V s *as. g W m + p -V w raw. g W »»«,=—+P a-Yod. g (11) (12) (13) Porosity of soil is defined by two parameters - void ratio e and porosity parameter r|. The total void ratio e is defined as the ratio of volume of pores to volume of solid particles V +V e = ■ and phases void ratio as e = ■ V s V - w, ' V ' s V V ■ (14) (15) (16) The porosity parameter r| is defined as the ratio of volume of water plus volume of air to volume of soil samples. Total: T| =• V +v V Phases: V ^=77 = V +v _w_a V +v +v V V _ a V V +V +V ' w a V V V +V +V ■ (17) (18) (19) The water content wa is defined as the ratio of the weight of water to the weight of soil particles w w-w-w-WA w ■■ w. w (20) The absolute water content wa is defined as the ratio of the weight of water to the total weight of sample w W W-W-W-W _w_ _ _a_s_aa W ~ W (21) The degree of saturation Sr is defined as the ratio of the volume of pores saturated with water to the volume of all pores S.=- V "H V +V ri +ri >v a • w t a (22) 1.1 Porosity determination methods The simplest method is the determination of porosity by saturation method (Fig. 1) /4/. In this standardised procedure, the beakers are first filled to the same mark with gravel, sand, silt or mixture of these three materials. Then the water is poured into each of the beakers until it reaches the top of each material. gravel > Fig. 1. Determination of porosity by saturation. Porosity is determined by dividing the volume of water that you were able to pour into the material by the total volume of that material. The result is expressed as a percentage. It dictates how much water a saturated material can contain and has an important influence on bulk properties of material, e.g. bulk density, heat capacity, seismic velocity, etc. = ^voi'd K. 100 % (23) where VVoid pore space volume Vtotai total volume There are many different porosity measurement methods. The imaging porosity method aims to identify and quantify different pore systems to determine the nature and abundance of matrix and macroporosity. Matrix porosity is characterised from digital images obtained from thin sections cut from core plugs /5/. The helium pycnometer method uses helium. The pycnom-eter consists of two chambers, connected by a tube with a valve in it. The idea Is to measure the pressure difference between the two containers, one of which has the sample material in it. The degree of porosity is determined by the difference in the pressures (due to porosity) caused by the opening of the valve at constant temperature. The porosity of the sample is the percentage difference between the grain volume and bulk volume, divided by the bulk volume /6/. Porosity can also be determined by other conventional methods such as adsorption method, infrared scattering, mercury porosimetry, capillary method, dielectric method, analytical method, proton nuclear magnetic resonance, chromatography and ultrasound method /7/, /8/. 74 V. Matko: Porosity Sensor Informacije MiDEM 33(2003)2, str. 73-78 The new porosity measuring method described in this paper uses a highly sensitive sensor with improved uncertainty of measuring results and reduced influence of disturbing noise signals /9/. In comparison to the helium pyc-nometer method it is a lot simpler. In addition, the water is not poured on the material. Instead, the soil or rock sample is immersed in the water. Most capacitive bridge methods can be adapted to three-terminal measurements by the addition of components to balance the ground admittances/10/, /11/. However, the balance conditions for these and the main bridge being interdependent, the balancing process can become very tedious. Also, the ratio signal/noise is supposed to be high. The well-known method is Miller's etalon /12/ which is designed to sense small changes in the = 4 pF capacitor from the phase change of a series-resonant circuit. The weakness of Miller's etalon is a greater sensitivity to phase noise than with the bridge method, which is due to higher frequencies (up to 45 MHz). An alternative approach has been described by Van Degrift /13/ who used very sensitive tunnel-diode oscillator systems for measuring extremely small capacitance changes. This gain in sensitivity is somewhat offset by a loss in stability. 2 The porosity sensor The porosity sensor uses sensitive capacitive-dependent crystals (40 MHz with stability of ±1 ppm in the temperature range from -5 to +55 °C) due to stability and the long-term repetition (Fig. 2). Two pseudo stochastic three-state signals xi(t) and X2(t) are used to influence the frequencies of the two quartz oscillators/14/, /15/. The frequency of oscillator 1 is 40 MHz and that of oscillator 2 is 40.001 MHz/16/, /17/. The output of the pulse-width modulator (EXOR) is a pulse-width signal which is compensated for temperature and voltage drift. are measured with impedance/gain phase analyser HP 4194A. Q2 Cx Fig. 2. Sensor structure. The sensor probe Cx is a capacitor on the outer surface of the glass test tube (Fig. 3) /18/. The crystal is used as a stable oscillation element whose substitutional electrical structure only is being changed through the variation of the series capacitance Cx. The values in the quartz substitutional electrical structure and the capacitance Cx = 5 pF Solid sample W Cx Fig. 3. Glass test tube. The change of the water level causes the change of capacitance and frequency change in oscillator 2 (Fig. 2, Fig. 3). The probe dependence df on the volume is shown in Fig. 4. The frequency measurement uncertainty is ±0.1 Hz. The results suggest that the change in frequency is proportional to the volume in the range 0 -1 ml. 1200 1000 800 X 600 t> 400 200 0 M —f— T=10'C —4—T=30°C 0.4 0.6 V (ml) Fig. 4. The probe dependence df on the volume with signals xi(t) and X2(t). 3 Reduction of the measurement uncertainty The uncertainty of the measuring results is improved by the direct digital method (DDM), which reduces the influence of disturbances/9/. Linear time-invariant system has been chosen due to signals xi(t) and X2(t), which form a special correlation function that is real-time independent. w=0 - cross-correlation function -weighting function (24) (t - u) - auto-correlation function T - measuring period 75 Informacije MIDEM 33(2003)2, str. 73-78 V. Matko: Porosity Sensor For every value of x, one equation with various numbers of elements is obtained. To calculate the value of the weighting functions g(0), g(1).....g(L), the equations are united in the system with L + 1 equations O xyi-P+Lj M-1) M0) M+0 O^C-P + i) . . . 0. c(-0 . ■ • c(0) eC+0 Á-P) ¿-1-L) Á-L) c(l -L) or its mathematical equivalent (25) The biggest negative time move rm/n = - Pand the biggest positive one tmax = M were used. The system of equations has thus P - L + M + 1 number of equations. If M = - P + 2L is chosen, L + 1 number of equations remain, so that 6 becomes a square matrix and we get Fig. 5. Functions ^^¡(x) and Oxy2(x). Consequently, the porosity is defined as a change of area between the functions <&xy2(i) and > whose change is defined by capacitance Cx and specially chosen test signals xi(t) and X2(t). In this way the test signal has been considered throughout the entire tmeas period, as well as the sign change compensation in the calculation of the cross-correlation function. Comparing to the measurements that are not DDM method based the improvement of the ratio signal/noise by = 30 dB is the most significant gain. g = G> o v ■O xy- (26) If P = L is determined, then the same number of values (symmetrical autocorrelation functions (AKF) because rm/n = -P = -L and rmax = M = L for the positive and negative r) is used to calculate (T ). The calculation of the weighting function is simplified if the input signal is white noise with the auto-correlation function as ®xx(0 = It follows that 8(t) *(0 = 1 for T = 0' 0 for |t| 1 3> d) :(0) ^ (0. (27) (28) (29) Having formulated (26) and having considered the measurement time tmeas which is to be as long as possible, we get the weighting function g(x) (29) /9/. 4 Porosity measurement Due to the specially chosen test signals xi(t) and X2(t) the function o j (t) begins in the origin of coordinates and ends on the X axis when r = tmeas (Fig. 5). 4.1 Calibration The frequency is simultaneously converted into volume units by calibrating the ratio between the frequency and the volume for each glass tube. Mercury, whose mass is measured at an error of 0.01 % (at known temperature) is used for calibration /19/. The mechanical nonlinearities of the glass tube diameter along the whole tube are taken into account. According to the producer's data these do not exceed 0.01 %. The dependence can be linearized by using the spline method. 4.2 The influence of temperature and measurement error The influence of temperature on measurements is considered in three ways. We must know the influence of the temperature on the measuring equipment, on the measuring medium in which the measurement is performed (i.e. the fluid in which the test is carried out), and the influence of the soil's temperature on its physical properties /19/. The temperature of the environment affects the linearity of the measuring sensor. Calibration is used to establish the measurement error of the sensor which is 0.03 %. If the relation between the output frequency and the volume is known (Fig. 4), we get V(T)=V(T0)+AV(T). (30) Equation (30) gives the correction of the measurement with respect to temperature changes. Temperature changes also affect the volume of the measured medium, i.e. of the 76 V. Matko: Porosity Sensor Informacije MIDEM 33(2003)2, str. 73-78 soil sample. Consequently, the change of volume due to temperature changes is expressed in the determination of the soil's specific gravity as follows y(T) = y(T0)+Ay(T). (31) In conditions of linear temperature relationship inside a certain temperature range it holds true that V(T) = Vs(T0)-(l+aK(T-Tj) where as is the temperature coefficient of soil. (32) The change of volume due to temperature changes in naturally humid soils is expressed as the sum of volume changes of all soil phases dV(T) = dV(T) + dV„(T) + dVd(T). (33) The total measurement error of the porosity sensor in relation to known individual partial influences such as glass tube nonlinearity, calibration with mercury, the influence of temperature on the sensor (Fig. 4), linearization ofaVon V, frequency measurement y(t) (Fig. 2), specific soil weight (31), change of water volume in the test tube and the change of sample volume dV(T) (33) does not exceed 0.1 % (10 - 30°C). This value was calculated on the basis of calibration data and the influence of temperature and measurement error. 5 Experimental porosity measurement To test the new method, volcanic rock samples, which are known for their porosity, were selected for experimental determination of porosity. Four characteristic samples approximately 1 ml in size and 1 g in weight were gathered near Puerto de Santiago, Mount Teide volcano (3715 m), Tenerife (Fig. 6). Fig. 6. Four typical porous volcanic rock samples of about 1 ml in size and 1 g in mass. All test samples were randomly selected. To determine the porosity of a random solid sample (at 20 °C), the sample is immersed in water contained in a test tube around which the capacitor Cx is placed (Fig. 3). The volume of the sample is measured. In the first case, the glass solid sample with ~ 0 % porosity was immersed (Fig. 7). 800 700 600 500 400 300 200 100 0 0 25 50 75 100 125 léo 175 200 t (ms) Fig. 7. Measurement of sample having ~ 0 % porosity. The frequency remained unchanged after immersion, which indicates that there was no air leak. In the second case, a dry randomly selected volcanic rock sample (weighting 0.821 g) was immersed in the water. Since the sample was porous, the air leaked, which was reflected in the dynamic change of frequency (Fig. 8). The transitional phenomenon caused by immersion ends in 1 ms. 100 125 150 175 200 t (ms Fig. 8. Air leak after sample immersion. The measurement is performed until the final state towards which the measurement limits is reliably predicted. Depending on the degree of porosity, this saturation limit is higher or lower as shown for the other three samples (Fig. 8). At known temperature the sample porosity can be determined V +V. ■ dry sample air (34) 77 Informacije MIDEM 33(2003)2, str. 73-78 V. Matko: Porosity Sensor The sample porosity on Fig. 8 was 23.8 %. The fastest measurement time without test signals is 1 (is. 6 Conclusion The porosity sensor using the capacitive-dependent crystals has been described and the dependence of df on the volume of the sensor probe has been presented. The porosity determination procedure includes the influence of test signals on the weighting function uncertainty. The formation of the cross-correlation function between the test signal x(t) and the system response y(t) decreases the influence of all disturbing signals that are not correlated to the test signal x(t) for = 30 dB /9/. Other advantages of the proposed method are high sensitivity, high stability, a series resonant circuit which is not composed of the elements L and C, the ratio signal/noise does not affect the accuracy of measurements, reduced disturbances due to the structure and the method, the long-term repetition, reduced hysteresis /17/ and low cost. It should be noted, however, that pairs of crystals with similar temperature characteristics should be used. The accuracy and repeatability are determined only with the temperature frequency difference of the crystal pairs /19/. 7 References /1/ P. Sheng, „Effective medium theory of sedimentary rocks," Phys. Rev. B., vol. 41, pp. 4507, 1993. /2/ S. Sakai, "Determination of pore size and pore size distribution," Journal of membrane science, vol. 96, pp. 91, 1994. /3/ K. Meyer, P. Lorenz, B. Bohl-Kuhn, and P. Klobes, "Porous solids and their characterization," Cryst. Res. Techn., vol. 29, pp. 903, 1994. /4/ A. Netto, "Pore-size distribution in sandstones," Bull. Appl. Math., vol. 77, pp. 1101, 1993. /5/ J. Fredrich, B. Menendez, and T.Wong, "Imaging the pore structure of geomaterials," Science, vol. 268, pp. 276, 1995. /6/ H. Franz, "Herstellung von Drucksensoren," Feinwerktechnik & Meatechnik 95, H. 3, pp. 145-151, 1987. /7/ J. Fripiat, „Porosityand adsorption isotherms," Fractal Approach to Heterogeneous Chemistry, Wiley, pp. 28, 1989. /8/ G. P. P. Gunarathne and K. Christidis, "Measurements of Surface Texture Using Ultrasound," IEEE Trans. Instrum. Meas., 50 (5), October, pp. 1144-1148, 2002. /9/ K. W. Bonfig, "Das Direkte Digitale Messverfahren (DDM) als Grundlage einfaoher und dennoch genauer und storsicherer Sensoren," Sensor Nov., pp. 223-228, 1988. /10/ M. C. McGregor, J. F. Hersh, R. D. Cutkosky, F. K. Harris, and F.R.Kotter, "New Apparatus at the National Bureau of Standards for Absolute Capacitance Measurement," IRE Trans. Instr. 1-7 (3-4), pp. 253-61, 1958. /11/ A. M. Thompson, "The Precise Measurement of Small Capacitances," IRE Trans. Instr. 1-7(3-4), pp. 245-53, 1958. /12/ G. L. Miller and E. R. Wagner, "Resonant phase shift technique for the measurement of small changes in grounded capacitors," Rev. Sci. Instrum. 61(4), pp.1267, 1990. /13/ C. T. Van Degrift, "Modeling of tunnel diode oscillators," Rev. Sci .Instrum. 52(5), May, pp. 712-723, 1981. /14/ K. Dmowski, "A new correlation method for improvement in selectivity of bulk trap measurements from capacitance and voltage transients," Rev. Sci. Instrum. 61(4), April, pp.1319-1325, 1990. /15/ M. Bertocco, A. Flammini, D. Marioli, and A. Taroni, "Fast and Robust Estimation of Resonant Sensors Signal Frequency," IEEE Trans. Instrum. Meas., 51 (2), April, pp. 326-330, 2002. /16/ V. Matko and J. Koprivnikar-a, "Capacitive sensor for water absorption measurement in glass-fiber resins using quartz crystals," IAAMSAD:South African branch of the Academy of Nonlinear Sciences, Proceedings, Durban, South Africa, pp. 440-443, 1998. /17/ V. Matkoand J. Koprivnikar-b, "Quartz sensor for water absorption measurement in glass-fiber resins," IEEE Trans. Instrum. Meas., 47 (5), Oct., pp. 1159-1162, 1998. /18/ M. Stucchi and K. Maex, "Frequency Dependence in Interline Capacitance Measurements," IEEE Trans. Instrum. Meas., 51 (3), Jun., pp. 537-543, 2002. /19/ R. C. Weast, "CRC Handbook of Chemistry and Physic," 67 th edition, Boca Raton, Florida, pp. E49-E52, 1987. Izr. prof. dr. Vojko Matko University of Maribor, Faculty of Electrical Engineering and Computer Science, Smetanova 17, 2000 Maribor, Slovenia E-mail: vojko.matko@uni-mb.si Prispelo (Arrived): 11.11.2002 Sprejeto (Accepted): 25.05.2003 78 UDK621.3:(53+54+621 +66), ISSN0352-9045 Informacije MIDEM 33(2003)2, Ljubljana OSNOVE TEORIJE OPTIČNIH PRESLIKAV, PRIREJENE ZA POTREBE SIMULACIJ FOTOLITOGRAFSKEGA PROCESA R. Osredkar Faculty of Computer Sciences and Faculty of Electrical Eng., University of Ljubljana, Slovenia Ključne besede: Fourireova optika, Frauenhoferjev uklon, MTF, fotolitografija, projekcijski poravnalniki, mikroelektronika Izvleček: V prispevku so predstavljene osnove teorije optičnih preslikav. Obravnavani so tisti aspekti Fourierove optike, Abbejeve teorije preslikav in teorije modulacijskih prenosnih funkcij (MTF), ki se nanašajo na preslikavo vzorcev s fotolitografske maske na s fotopolimerom prevlečeno rezino s projekcijskimi poravnalniki. Basics of Optical Imaging Theory Applied to the Photolithographis Process Simulation Key words: Fourier optics, Frauenhofer diffraction, MTF, photolithography, projection aligners, microelectronics Abstract: Lithography is the cornerstone of modern IC manufacturing, and lithography tools and process characterization at the core of the lithography process engineering. Most of the ICs today are manufactured by optical photolithography. As the dimensions of the features to be fabricated on the wafer approach 0.1 ^m the classical limits of resolution of optical tools used in photolithography are approached. Understanding and optimization of the performance of the lithographic process are thus becoming less accessible by the empirical methods traditionally used in IC manufacturing process development and have to be complemented by different computer simulation tools. Such tools are based on Fourier optics to describe the performance of exposure systems, and for their use a basic understanding of the underlying optical theory is required. In this tutorial these basics are covered, with the intenion to facilitate a study of more advanced literature. All of the projection exposure systems used in IC manufacturing industry today are diffraction limited optical instruments. Consequently Frauenhofer diffraction theory is used to describe their performance. This has important consequences for imaging the fine mask patterns on the photoresist covered wafer. In order to understand the ralation between the (spatial) Fourier transform of the mask pattern and the diffraction image formed by the objective lens in its focal plane, it is instructive to compare the Fourier transform of a pulse function and the analytical expression for the diffraction image of a line source. It can immediately be seen, that they are equal. This conclusion can be generalized to the more complex case of mask imaging. Thus the far-field electric field intensity E(yu,Zff) is given by E(yfi.Zff) = F[f(y,z)] where f(y,z) is mask transmittance function, and F Fourier transform operator. The objectve lens performs an inverse Fourier transform of E(yff,Zff), resulting in an image of the mask in the image plain of the objective lens, where the wafer is positioned. Field intensity distribution E(yi,Zi) of the image in the wafer plane is E(yi|Zi) = F-1[E(y„,z„) P0(fy, fz)I = F1{F[E(y,z)] P„(fy, «} where F_1 inverse Fourier trasform operator. The pupil function P0(fy, f2) of the objective lens is introduced into the expression in order to take account of finite dimensions of the lens. From this expression the well known resolution criteria of a projection system can be extracted. Another basic optics concept allowing modeling of the aerial image on the surface of the photoresist film is the modulation transfer function (MTF). MTF is basically a measure of the contrast in the aerial image produced by the exposure system. It is also governed by the diffraction effects and MTF is therefore a function of the normalized spatial frequency ^ of the image. The resolution and the MTF(^) characterise performace of an exoposure tool, and have to be Incorporated in a simulation. An implementation of these ideas In FOLIS, a photolithograhy simulation tool developed at the Microelectronics laboratory of the Faculty of Electrical Eng., University of Ljubljana, is reporte elsewhere /5/. Uvod Fotolitografija je eden od temeljev modernih postopkov izdelave integriranih elektronskih vezij in fotolitografska osvetljevalna orodja njeno središče. Velika večina takšnih orodij so danes projekcijski poravnalniki. Minimalne (tako imenovane kritične) dimenzije na sodobnih integriranih vezij segajo v področje velikosti 0,1 jxm, kar je povsem na meji, če ne celo pod njo, ločljivosti osvetljevalnih orodij. Zato predstavljajo postopki preslikave in osvetljevanja velik izziv za razvijalce mikroelektronskih postopkov in dodobra uveljavljeni, empirični pristop k reševanju litografskih problemov, ki se pojavljajo pri njihovem delu, jim v resnici ni več povsem kos. Toda uspešno ga lahko dopolnijo različna programska orodja za simulacijo fotolitografskega postopka. Njihova uporaba pa zahteva vsaj osnovno poznavanje optične teorije. 79 Informacije MIDEM 33(2003)2, str. 79-85 R. Osredkar: Osnove teorije optičnih preslikav, prirejene za potrebe simulacij fotolitografskega procesa Vsi projekcijski osvetljevalni sistemi, ki se danes uporabljajo v mikroelektronski industriji, so naprave, ki jim kvaliteto preslikave omejujejo uklonski pojavi. Te obravnava teorija Frauenhoferjevega uklona (uklona v daljnem polju), ki ga najpreprosteje simuliramo v okvirih Fourierove optike. Tudi če fotolitografsko preslikavo okarakteriziramo s prenosno funkcijo sistema, se upoštevanju uklonskih pojavov pri preslikavi ne moremo izogniti. Vse omenjene teme so v teoriji optike dobro in že dolgo časa poznane ter jih obravnava vrsta knjig /na primer 1, 2/ ter priročnikov /3/. Vendar se zdi, da je v praksi njihova uporaba omejena, morda v duhu pregovora, da v gozdu ni videti dreves. Fizikalni temelji sicer kompleksne optične teorije pa so razmeroma lahko razumljivi tudi v okviru znanj, ki jih razvojni inženir, delujoč na področju mikroelektronske fotolitografije, že ima. Namen tega prispevka je, da pravvtem okviru predstavi osnove relevantne optične teorije in tako olajša prvi korak pri poglobljenem študiju zahtevnejše literature. V prispevku zato ni govora o tehničnih podrobnostih projekcijskih osvetljevalnih naprav itd. Te so na voljo v literaturi /na primer v izboru literature v 4/. Prav tako v njem ni govora o simulacijskih orodjih, ki jih obravnavamo drugje /5/, pač pa so poudarjeni prav osnovni fizikalni pojmi optične teorije preslikav. Fourierova transformacija pulzne funkcije Fourierov integral neke funkcije f(x) je definiran /6/ kot 1/2 A{k)~ J/(x)cosAx<& = jE0coskxdx-^^-sinkL/2 % jA(k)c oskxdk + m kx dlc kjer sta A(k)= J f(x)coskxdx ¡n B{k)- J/(x)sin kx dx Podobnost gornjih izrazov z morda nekoliko bolj domačimi izrazi za Fourierovo vrsto je očitna, če se le spomnimo, da je integral limita vsote neskončne vsote. Količini A(x) in B(x), ki ju lahko razumemo kot amplitudi kosinusnih in sinusnih prispevkov k funkciji f(x) v intervalu od k do k+dk, se imenujeta kosinusna in sinusna transformacija funkcije f(x). Oglejmo si Fourierovi transformaciji funkcije, ki predstavlja pravokoten pulz z dolžino L: f(x) = E0l če je |x| < L/2 0, če je J x | > L/2 Ker je f(x) soda funkcija, je njena sinusna transformacija B(k) enaka 0, medtem ko je -l/2 Če v zadnjem izrazu ulomek v števcu in imenovalcu pomnožimo z L ter člene nekoliko preuredimo, je končni izraz za Fourierovo transformacijo pulzne funkcije A(k) = E0L smkL/2 kL! 2 _ , .. smkL/2 „ . , , Funkcijo v optiki srečujemo tako pogosto, da zanjo kL/2 običajno uporabljajo poseben simbol, sine kL/2. Fourierovo transformacijo pulzne funkcije torej zapišemo kot A(k) = E0L sine kL/2 Na sliki 1 sta prikazani pulzna funkcija f(x) in njena Fourierova transformacija. f(x) F(k)=A(k) Slika 1: Pulzna funkcija in njena Fourierova transformacija. Uklon Če neko EM valovanje (svetlobo) prestrežemo z ravnim zaslonom v katerem je izrezana dolga, ravna reža, se skoznjo del vpadnega valovanja širi v polprostor za zaslonom. Kako to valovanje opišemo? Nalogo poskušamo rešiti s pomočjo Huygens-Fresnelovega načela/1 /, ki zagotavlja, da širjenje valovanja lahko opišemo tako, da si neko valovno čelo valovanja zamišljamo razdeljeno na primerno majhne dele, ki so vsak izvor sekundarnih, krogelnih valovanj. Ta imajo isto valovno dolžino kot vpadno valovanje, kjer koli v prostoru za izbranim valovnim čelom pa je nato vrednost nihajoče količine (pri EM valovanje na primer velikost električnega polja, oz. električna poljska jakost E) določena s superpozlcijo (nekoliko grobo rečeno, vsoto) prispevkov sekundarnih valov. Pri seštevanju moramo seveda upoštevati amplitude in faze posameznih prispevkov, kar nalogo v splošnem zelo zaplete. Sorazmerno preprosto jo lahko rešimo pravzaprav le v dveh primerih. Prvi je tisti pri katerem točka v kateri iščemo valovanje, od izbrane valovne fronte ni preveč oddaljena (v tako imenovanem bližnjem polju), drugi pa, če je točka od nje zelo oddaljena (v daljnem polje). V zvezi s projekcijskim osvetljevanjem nas zanima le drugi primer. Preden se resnično lotimo seštevanja prispevkov sekundarnih valov k polju v toči T, definirajmo geometrijo problema: 80 R. Osredkar: Osnove teorije optičnih preslikav, prirejene za potrebe simulacij fotolitografskega procesa Informacije MIDEM 33(2003)2, str. 79-85 na zaslon padajoče valovanje naj se širi v smeri x, zaslon pri x = 0 naj leži v ravnini y,z, torej naj bo vzporeden valovnim frontam upadlega valovanja in reža v njem, ki ima širino L, naj leži, simetrično na os x, v smeri z. Če je dolžina reže mnogo večja od njene širine, je očitno, da mora biti rešitev neodvisna od koordinate z. Z drugimi besedami, rešitev iščemo le v ravnini x,y, kar 3-dimenzionalno nalogo praktično prevede v 2-dimenzionalno in jo znatno poenostavi. Za valovno čelo, ki je izhodišče računa, izberemo ravnino zaslona. Režo si moramo torej zamisliti razdeljeno na primerno majhne dele, ki so izvori sekundarnih valov in v neki točki T za zaslonom sešteti njihove prispevke k polju E. Električno polje ravnega EM valovanja, ki potuje v pozitivni smeri osi x pred zaslonom, opisuje enačba E(x) = E0 sin(cot - kx) kjer sta cd krožna frekvenca (2nv) in k valovni vektor (2n/X, Xje valovna dolžina valovanja). Valovanje, ki se širi iz točkastega izvora, pa opisuje enačba E = (A/r) sin(cot - kr) kjer sta A tako imenovana jakost izvora in r razdalja od izvora do točke T v kateri valovanje opazujemo. V primeru, ki ga obravnavamo, r leži v ravnini x,y. Podobnost izrazov za ravno in krogelno valovanje je očitna, pomembna razlika med njima je le v faktorju 1/r, ki pri slednjem opisuje zmanjševanje amplitude polja z razdaljo. Režo si mislimo po širini razdeljeno na majhne dele dy. Prispevek vsakega izmed njih k skupnemu polju v točki T je dE = (Al/t) sin(cot - kr) dy kjer je Al linearna jakost izvora, A/L. Da bi dobili celotno polje, moramo gornje prispevke integrirati po celotni širini reže. V primeru daljnega polja, pri katerem je širina reže L mnogo manjša od r, faktor 1 /r brez zadrege lahko zamenjamo z 1 /R, kjer je R razdalja od koordinatnega izhodišča (sredine reže) do točke v kateri računamo polje valovanja. Tega pa ne moremo storiti pri prostorsko spremenljivi fazi valovanja kr (torej v izrazu 2nr/X), saj pri njej razdalje očitno merimo v enotah valovne dolžine in je zato faza na majhne spremembe razdalje mnogo občutljivejša kot amplitu-da. Vendar pa pri računu daljnega polja r v izrazu za fazo lahko zamenjamo s približkom r= R-ysin0 pri čemer je y koordinata izvora dy v reži (slika 2). Po tej zamenjavi je izraz za skupno električno polje v točki T R L/2 Jsinjatf - k(R - ^sinO -L/2 in ga (z zamenjavo spremenljivk) zlahka integriramo: zaslon Slika 2: Uklon svetlobe na reži s širino L. A£sin[(k/2)sin9] , , * (kL/2>in0 Smia)' kR)'°Zh oziroma kjer smo (kL/2)sin 0 zapisali kot /3. Primerjava izrazov za električno polje svetlobe, ki jo sevata reža in točkast izvor, pokaže, daje EM valovanje, ki izhaja iz reže, glede časovne odvisnosti in upadanja amplitude z razdaljo podobno valovanju točkastega izvora, vendar pa ni izotropno - v smereh, torej pri kotih 0, v katerih ima funkcija sinc(3 vrednost 0 ga enostavno ni. Iz slike 1 je razvidno, da se to prvič zgodi, ko je vrednost njenega argumenta n, torej pri n = (kL/2)sin0 = (2n/X)(L/2) sin0, oz. Lsin0 = X V slednjem takoj prepoznamo izraz, ki ga za smer uklon-skega minima prvega reda za uklon svetlobe na ozki reži s širino L daje elementarna teorija uklona /7/. Moteči časovni odvisnosti električnega polja se izognemo tako, da v izrazu zanj sin(roi-&?) zamenjamo z njegovo 1 časovno povprečno vrednostjo, ki je Po takšni zamenjavi postane enakost (do multiplikacijskega faktorja) izrazov za električno polje valovanja, ki ga seva ozka reža v zaslonu, in tistega za Fouriereovo transformacijo pulzne funkcije očitna. Enakost ni naključna. Z razširitvijo gornje izpeljave na 2-dimenzionalne reže v zaslonu in njeno manjšo po-splošitvijo se da pokazati, daje uklonska slika svetlobe, ki prehaja skozi zaslon s poljubno razporeditvijo in obliko rež, v daljnem polju, vedno enaka Fourierovi transformaciji funkcije, ki opisuje porazdelitev, obliko in propustnost rež na zaslonu. Ugotovitev je za analizo in modeliranje preslikav v projekcijskih poravnalnikih, ki se uporabljajo v mikroelek-tronski industriji, ter drugod v optiki ključna. In seveda tudi praktična, ker s pomočjo računalnikov Fourierove transformacije poljubne prostorske funkcije lahko izračunamo brez velikih zapletov. 81 Informacije MIDEM 33(2003)2, str. 79-85 R. Osredkar: Osnove teorije optičnih preslikav, prirejene za potrebe simulacij fotolitografskega procesa Transmisijska funkcija Maske, ki se uporabljajo pri izdelavi integriranih vezij, so navadno ravne, kvarčne plošče prevlečene stanko plastjo kroma. Na mestih, kjer na maski ni kromove plasti, je ta za UV svetlobo izvora prozorna, na prekritih mestih pa zanjo povsem neprepustna. Kontrast med svetlimi In temnimi deli maske je velik in zato lahko strukturo na maski zelo natančno opišemo z digitalno transmisijsko funkcijo f(x,z), ki ima vrednost 0 kjer maska nI prozorna In 1 na njenih prozornih delih. Porazdelitev električnega polja svetlobe, ki jo določa takšna maska, je v daljnem polju preprosto E(ydp,Zdp) = F[f(y,z)] kjer F pomeni Fourierovo transformacijo. Električno polje je pri preslikavah navadno manj zanimiva količina od gostote energijskega toka, ki je sorazmerna kvadratu električnega polja. Različnim multiplikacijskim faktorjem v izrazih za gostoto toka se pogosto ognejo z vpeljavo iradiance I, ki je le kvadrat polja. Za kotno odvisnost Iradiance v primeru dolge reže torej velja 1(6) = losinc2 (3 , kjer je l0 Iradianca v smeri optične osi (smeri x). Za masko, ki jo definira transmisijska funkcija maske f(y,z), podaja ira-dianco v daljnem polju izraz: l(ydp,Zdp) = | F[f(y,z)] |2 kjer so f goriščna razdalja objektiva, a razdalja od maske (predmeta) do glavne ravnine objektiva in b razdalja od glavne ravnine objektiva do ravnine slike. Proces nastanka slike si morda najlaže pojasnimo tako, da si točke v gorišč-ni ravnini objektiva, kjer se sekajo vzporedni snopi žarkov z maske, predstavljamo kot še ene izvore Huygensovih sekundarnih valov, ki interferirajo v ravnini slike. Prav ta druga interferenčna slika je slika predmeta, ki jo da objektiv (slika 3). Nastanek slike je torej posledica dvojnega uklonskega procesa: najprej uklona ravnega valovanja na predmetu in nato uklona valovanj, ki po prvem uklonu potujejo v različnih smereh, na objektivu. Tako je jasno, da pri preslikavi objektiv naredi Inverzno Fourierovo transformacijo uklonske slike predmeta. Abbejeva teorija preslikave Pri osvetljevalnih sistemih, ki jih v industriji uporabljajo za preslikavo vzorcev z mask na silicijeve rezine, nas seveda zanimajo predvsem gostote energijskega toka (ali iradianca) na površini fotopolimera. Uklonska slika maske v daljnem polju je, kot smo videli, enaka Fourierovi transformaciji njene transmisijske funkcije in bi jo, v načelu, lahko pre-stregli in opazovali na dovolj oddaljenem zaslonu. To razdaljo zelo skrajšamo, če za masko postavimo lečo (objektiv). Ker so vsi žarki, ki iz predmeta izhajajo v smeri, določeni s kotom 0 (torej kotom med smerjo razširjanja valovanja in optično osjo sistema), med seboj vzporedni, se po prehodu skozi objektiv sekajo v eni točki. Z drugimi besedami, v goriščni ravnini objektiva nastane Frauenho-ferjeva uklonska slika predmeta. Ker je ta slika Fourierova transformacija maske, včasih o objektivu govorijo kot o transformacijski leči in o ravnini v kateri nastane transformira-na slika kot o transformacijski ravnini. V našem primeru sta goriščna ravnina objektiva in njegova transformacijska ravnina seveda Ista ravnina. Na zaslonu, ki bi ga postavili v to ravnino, bi Interferenčno sliko lahko prestregli in opazovali. Če takšnega zaslona ni, pa se svetloba širi še naprej in v neki drugI ravnini, imenovani ravnina slike, rekonstruira sliko maske. Položaje maske, glavne ravnine objektiva, njegove goriščne ravnine In ravnine slike na optični osi povezuje enačba leče 1/f = 1/a + 1/b ravnina predmeta ravnina slike Slika 3: Nastanek slike je dvojni uklonski proces: slika predmeta nastane zaradi interference svetlobe, ki izhaja iz transformacijske ravnine. M je povečava preslikave. Ločljivost Najbrž je očitno, da objektiv lahko rekonstruira popolno sliko predmeta le, če zajame njegovo celotno uklonsko sliko. Praktično je to seveda nemogoče, saj pri uklonu glede velikosti kotov 9 ni nobenih omejitev, vsi objektivi pa imajo končne premere. Če leži predmet na razdalji a pred objektivom, ki ima polmer R, je največji kot med žarki, ki izhajajo iz (majhnega) predmeta in jih objektiv še zajame ©maxtakšen, daje tgQmax = R/a Razmerje R/a se imenuje numerična apertura (NA) sistema. (NA iz tehničnih razlogov navadno definirajo kot sin ©max , razlika na tem mestu ni posebno pomembna.) Če želimo z objektivom preslikati nek predmet, recimo režo, s 82 R. Osredkar: Osnove teorije optičnih preslikav, prirejene za potrebe simulacij fotolitografskega procesa Informacije MIDEM 33(2003)2, str. 79-85 tako majhno širino L, daje smer prvega uklonskega minimuma, ki ga določa kot 0 ravno enak numerični aperturi objektiva, torej sin© = A./L = NA smo očitno na meji resolucije objektiva. Pri še manjših predmetih (ožjih režah) objektiv zajame le še svetlobo ničtega uklonskega maksimuma (torej svetlobo, ki se na reži ne ukloni in skozi sistem potuje v smeri optične osi), v tej pa ni nikakršne informacije o velikosti predmeta. Ta se skriva le v položajih minimovv uklonski sliki in če teh v svetlobi, ki jo zajame objektiv, ni, objektiv predmeta ne more rekonstruirati. Vpliv omejene kotne velikost objektiva navadno vključijo v modeliranje preslikave z zenično (pupilno) funkcijo objektiva, P0(fy, fz), ki ima vrednost 1, če je (f2y + f2z)1/2 < NA/A, in 0, če je (f2y + f2z)1/2 > NA/A, , kjer je fytako imenovana prostorska frekvenca uklonske slike na objektivu: fy = y0b/al fz je definirana na enak način. Prostorske frekvence, ki jih objektiv lahko transformira (preslika) so očitno omejene z vrednostjo fmax = NA/A in zenična funkcija to odraža. Končna velikost objektiva pri preslikavi predmetov z velikimi prostorskimi frekvencami (kar pomeni z majhnimi dimenzijami) igra isto vlogo kot, na primer, nizkopasovni filter pri prenosu ostrih pulznih signalov. Takšen filter signale (seveda v časovni domeni) zaobli, objektiv pa podobno (v prostorski domeni) ne preslika podrobnosti predmeta, ki so skrite v velikih prostorskih frekvencah njihove uklonske slike. Zenično funkcijo vključimo v izraz za preslikavo in porazdelitev električnega polja na mestu slike zapišemo kot E(ys,zs) = F1[E(y0,z0) P0(fy, fz)] = F1{F[E(y,z)] P0(fy, fz» kjer je F-1 inverzna Fourierova transformacija. Iradianca na mestu slike pa je, kot vedno, | E(ys,Zs) |2. Povečanje ločljivosti Najmanjšo velikost predmetov, ki jih z nekim projekcijskim poravnalnikom lahko preslikamo z maske na fotopolimer in rezino, torej v načelu omejuje končna ločljivost optičnih sistemov. Vendar sta poznana vsaj dva načina kako povečati ločljivost projekcijskih sistemov /4/. Prvi temelji na dejstvu, da je uklonska slika, na primer reže, simetrična glede na ravnino x,z in da zato vključuje informacijo o velikosti reže dvakrat: enkrat v uklonskih minimih v smeri osi +y ter drugič v minimih v smeri -y. Za verno preslikavo pa takšna dvojnost pravzaprav ni potrebna in v načelu za rekonstrukcijo slike zadošča že uklonjena svetloba, ki se od predmeta širi k objektivu le, recimo, nad optično osjo sistema. Če bi objektiv z določeno NA za njegov polmer premaknili vzdolž osi y, bi po premiku njegov spodnji del zajel le še na maski neuklonjeno svetlobo, njegov zgornji del pa dodatno še uklonjeno svetlobo višjih redov. Zaradi vključitve te svetlobe v preslikavo bi bila tudi slika reže ostrejša. Prav isto bi seveda dosegli z objektivom, ki ima 2 krat večji polmer (in ustrezno večjo NA), ter z zaslonom, ki bi zastrl del objektiva pod optično osjo. Eno ali drugo bi povečalo ločljivost, toda tudi v preslikavo vneslo nesprejemljive abe-racije. Podobno bi enako povečanje ločljivosti (iz istega razloga in s podobnimi abracijami) brez premikanja ali zastiranja objektiva dosegli tudi tako, da bi masko osvetlili pod kotom 0max- Dejansko so koti izvenosnega osvetljevanja, ki še omogočajo nepopačeno preslikavo, hkrati z nekoliko večjo ločljivostjo, mnogo manjši od 0max, toda tehnika je pri konstrukciji projekcijskih poravnalnikov često uporabljena. Povsem drugačna tehnika povečevanja ločljivosti projekcijskih osvetljevalnih sistemov temelji na manipulaciji faze, s katero uklonjena svetloba izstopa iz maske /8/ . Za nek del maske lahko postavimo planparalelno ploščico iz snovi z lomnim količnikom n in debelino t, izbrano tako, da del svetlobe, ki gre skozi ploščico, glede na svetlobo, ki gre mimo nje, zaostane za fazni kot n. Debelino t fazne ploščice določa enačba 2(n-l) Deli svetlobe, ki gredo skozi fazno ploščico, pri rekonstrukciji uklonske slike seveda sodelujejo z za n spremenjeno fazo, ali z drugimi besedami, električno polje teh delov svetlobe je pomnoženo s faktorjem -1. S primerno razporeditvijo faznih ploščic po različnih delih maske je mogoče doseči, da se električno polje na določenih delih slike na rezini izniči. S fazno masko torej lahko dosežemo, da ostanejo deli rezine, ki bi bili pri osvetlitvi z navadno masko osvetljeni, neosvetljeni. Princip delovanja faznih mask je prikazan na sliki 4. V okviru Fourierove optike je maska amplituda polja za masko amplituda polja na rezini fazni zasuk Slika 4: Princip povečanja ločljivosti preslikave z uporabo fazne maske (po /8/). njihov učinek na ločljivost prav enostavno pojasniti: 180-stopinjski fazni premiki na primerno izbranih delih maske razpolovijo osnovno prostorsko frekvenco vzorca na maski (kar je razvidno iz slike) in zato lahko objektiv z določeno NA, ki sicer deluje na meji ločljivosti, takšne dele maske preslika z velikim kontrastom. Kakšna mora biti razporedi- 83 Informacije MIDEM 33(2003)2, str. 79-85 R. Osredkar: Osnove teorije optičnih preslikav, prirejene za potrebe simulacij fotolitografskega procesa tev faznih ploščic na maski s preprosto periodično strukturo je očitno, v splošnem pa načrtovanje fazne maske ni enostavna naloga. Na slikah v /5/ so prikazani primeri simulacije (s programom FOLIS) faznih mask z nekoliko bolj zapleteno strukturo. MTF Ločljivost nekega optičnega instrumenta je vsekakor pomembno merilo njegove zmogljivosti, nikakor pa ne edino. Fotolitograske maske tipično niso objekti s preprosto periodično strukturo, katere preslikavo na rezino bi omejevala le ločljivost projekcijskega poravnalnika. Na njih so navadno objekti različnih dimenzij, z bolj ali manj ostrimi vogali itd. in pravi izziv za konstruktorje osvetljevalnih naprav je kontrastna preslikava celotne maske in ne le zadovoljiva preslikava njenih najmanjših delov. Priljubljena analogija preslikavi realne maske je s področja elektroakustike: ocenjevati kvaliteto neke HiFi naprave le po najvišji frekvenci, ki jo zmore reproducirati, je očitno precej pomanjkljivo. Veliko več bi o kvaliteti reprodukcije povedal nek kriterij, ki podaja zmogljivosti naprave v njenem celotnem frekvenčnem območju. Kot takšno merilo kvalitete preslikave se je v optiki uveljavila modulacijska prenosna funkcija (modula-tion transfer function, MTF) /3/. Če ob prehodu svetlobe skozi fotolitografsko masko pustimo podrobnosti sipanja itd. povsem ob strani, lahko prehod obravnavamo kot modulacijo curka svetlobe. Na mestih, kjer maska svetlobo prepušča, ostaja gostota svetlobnega toka (oz. iradianca) nespremenjena, na mestih, ki so zakrita s plastjo kroma, pa maska svetlobe sploh ne prepušča. Na osnovi te ugotovitve smo že definirali transmisijsko funkcijo maske in podobno definiramo tudi modulacijo Mm svetlobnega toka, ki prehaja skozi masko, kot p./r _ IoM ItM m - IoM ^ ItM kjer sta I0m največja in Um najmanjša gostota toka po prehodu svetlobe skozi masko. Povsem enako definiramo modulacijo svetlobe v ravnini slike Mc I oŠ 'I tS IoS+ItS MTF optičnega sistema je definirana kot MTF = Ms/Mm in meri kontrastnost slike pri preslikavi. Ker je v praksi tran-smisijska funkcija maske domala idealno digitalna in je zato Mm zelo natančno enak 1, je prenosna funkcija sistema praktično enaka Ms. Iz opisa mehanizma preslikave bi moralo biti očitno, da je MTF funkcija velikosti struktur na maski, ki jih želimo preslikati. Če so te velike, da preslikava verno, zelo kontrastno sliko predmeta in je vrednost MTF blizu 1. Pri strukturah, ki so istega reda velikosti kot ločlji- vost projekcijskega poravnalnika, pa je vrednost MTF blizu 0. Velikost struktur na maski opisuje njena prostorska frekvenca u, ki je za masko, podobno uklonski mrežici, navadno podana kar kot število linij na milimeter. Frekvenca u seveda ni enaka (na žalost pa se enako imenuje) prostorski frekvenci predmeta fx, ki smo jo srečali pri obravnavi uklona. Dejansko MTF navadno podajajo kot funkcijo normalizirane prostorske frekvence i,, ki je kvocient obeh, to je % = u/fx Izpeljava MTF za nek optični sistem je sorazmerno nazorna in nezahtevna le za lečo, ki je pri projekcijskih osvetljevalnih sistemih pravzaprav nikoli ne srečamo, namreč za idealno cilindrično lečo. Zato nam v to kislo jabolko ni treba ugrizniti, omenimo le, daje pri taki leči izpeljava nezahtevna zaradi preproste, cilindrične simetrije rež na maski in leče. Uklonsko omejena MTF za takšno lečo brez abera-cij, pri monokromatski svetlobi je MTF© = (1 - $ Za sferično lečo, pri istih pogojih, je MTF MTF = - [arccos® Ji-Z,2 1 TZ Analogija med obema izrazoma je morda opazna, njuna podobnost na grafu obeh funkcij pa očitna (slika 5). Omeniti je treba, daje pri sferični leči in krožnem predmetu, ki ga leča preslikuje, (kotna) prostorska frekvenca fr definirana nekoliko drugače kot pri reži, fr = (2emaxSin 0max)A 0 .2 A .6 .8 1.0 Normalizirana prostorska frekvenca Slika 5: MTF za okroglo in pravokotno zaslonko objektiva. 84 R. Osredkar: Osnove teorije optičnih preslikav, prirejene za potrebe simulacij fotolitografskega procesa Informacije MIDEM 33(2003)2, str. 79-85 Definicija prenosne modulacijske funkcije nekega sistema, kot je opisana, strogo velja le za preslikavo s koherentno svetlobo. Koherenčni pogoj za nek izvor svetlobe je d sincp « X/2 kjer sta d premer izvora in (p največji kot med žarkom, ki ga optični sistem še zajame, in optično osjo sistema. Realni izvori končnih dimenzij koherenčnemu pogoju lahko zadostijo le, če ležijo v neskončnosti, pri takšnem položaju izvora pa je gostota energijskega toka na mestu maske seveda 0. V praksi se problem koherence izvora navadno reducira na razmerje numeričnlh apertur kondenzorske in projekcijske optike fotolitografskega sistema in je stopnja nekoherence s definirana kot S = NAkon/NApr s za idealno koherenten izvor, ali izvor v neskončnosti je torej 0. Na prvi pogled bi morda sodili, da je prav takšen najbolj primeren za potrebe optične litografije, vendar nI tako. Videli smo že, da z izvenosnim osvetljevanjem masko, ki nosi strukture z veliki prostorskimi frekvencami (zelo majhne strukture), natančneje preslikamo kot z osvetljevanjem v osi. Tudi delna nekoherenca Izvora privede do tega, da vsa svetloba na masko ne pade pod natanko pravim kotom. Zaradi tega se uklonska slika maske razprši v večji kot kakor pri koherentni osvetlitvi, takšen, ki ga NA objektiva ne zajame več. Slika maske je zato na ravnini silicijeve rezine seveda nekoliko bolj razmazana. Zaradi delne izvenosne osvetlitve pa objektiv hkrati zajame tudi del uklonjene svetlobe z drobnih struktur na maski, ki bi jo sicer povsem izločil in jih preslika. Preslikava z delno nekoherentno svetlobo je zato ostrejša. Stopnjo koherentnosti izvora se da vključiti v MTF /9/, toda analitični izraz za MTF(^,s) nespecialistu na žalost ne pove prav ničesar. Ponovno si pomagamo z grafom. Na sliki 6 je prikazana simulacija MTF(£,s) s programom FOLIS za nek dejanski projekcijski osvetljevalni sistem. Povsem očitno je, da vrednost MTF(^,s) pri normaliziranih prostorskih frekvencah ki so večje od 0,5, narašča z naraščajočo MTF(r.0.J5) ~ 0.2 - " 0 M 0.< 0.6 0.8 1 Slika 6: Simulacija MTF s programom FOLIS za projekcijski osvetljevalni sistem UTS 1100 z Wynne-Dysonovo optiko. stopnjo nekoherentnosti. Praviloma takšno odvisnost MTF(<;,s) od s opazimo pri vseh projekcijskih poravnalnikih. To pomeni, da je običajno pri velikih prostorskih frekvencah predmeta (maske) kontrastnost slike pri preslikavi z delno koherentno svetlobo večja kot pri preslikavi s koherentno in preslikava majhnih objektov z maske na površino rezine boljša. Le omenimo, da nelinearni odziv fotopolime-ra na osvetlitev, kontrast v fotopolimer prenesene fizične slike lahko še Izboljša. Še boljši približki MTF nekega optičnega sistema vključujejo tudi efekte globine fokusa, abe-racij optičnega sistema, odstopanj optičnih elementov sistema od idealne oblike itd. Vse te popravke v MTF navadno vključijo kot fazno aberacijo ep sistema, ki ga torej oka-rakterizira prenosna funkcija treh spremenljivk, MTF(^,s,cp). Zaključek Vse predstavljene metode analize optičnih preslikav se v takšni ali drugačni obliki uporabljajo v simulacijskih orodjih za modeliranje fotolitografskega osvetljevanja rezin. V praksi jih dopolnjujejo računalniške metode hitrega Fourirovega obrata (FFT), ki so danes postale povsem vsakdanje, in množica empiričnih modelov različnih podrobnosti preslikave. Združiti vse to v uporabno simulacijsko orodje je zahtevna naloga, ki je brez poznavanja osnov optične teorije nerešljiva. V Laboratoriju za mikroelektroniko, Fakultete za elektrotehniko, Univerze v Ljubljani je bilo razvito simulacijsko orodje FOLIS v katerem je opisana teorija implementirana. Literatura /1./ E.Hecht and A. Zajac, Optics, second printing, Addison-Wesley Publishing Co., Reading, MA. USA, 1977 /2./ E. L. O'Neil, Introduction to Statistical Optics, Addison-Wesley Publishing Co., Reading, MA. USA, 1963 /3./ Optics Guide 3, Melles Griot, Irvine, CA, USA, 1985 /4./ J.D. Plummeretal., Silicon VLSI Technology, Prantice Hall, Upper Saddle River, N.J., USA, 2000 /5./ I. Macarol, R. Osredkar, FOLIS, a PC Compatible Photolithography Simulation Tool, to be published in inf. MIDEM, Vol 33, March 2003 /6./ Bronštejn et. al., Matematični priročnik, Tehniška založba Slovenije, Ljubljana, SI, 1997 /7./ J. Strnad, Fizika, drugi del, DZS, Ljubljana, SI, 1978 /8./ M.D. Levenson et al., Improving Resolution in Photolithography with a Phase Shifting Mask, IEEE Trans. Elec. Dev., Vol. ED-29, 1982 /9./ A. Offner, Wavelength and Coherence Effects on the Performance of Real Optical Projection Systems, Photographic Sc. Eng., Vol. 23, No. 6, Nov./Dec., 1979 Radko Osredkar FRI in FE Univerze v Ljubljani Tržaška 25, SI 1000, Ljubljana, Slovenia e-mail: radko.osredkar@fri.uni-lj.si Prispelo (Arrived); 20.11.2002 Sprejeto (Accepted): 25.05.2003 85 UDK621.3:(53+54+621 +66), ISSN0352-9045 Informacije MIDEM 33(2003)2, Ljubljana HW/SW PARTITIONED OPTIMIZATION AND VLSI-FPGA IMPLEMENTATION OF THE MPEG-2 VIDEO DECODER Matjaž Verderber, Andrej Žemva University of Ljubljana, Faculty of Electrical Engineering, Ljubljana, Slovenia Key words; MPEG-2 video decoder, FPGA implementation, optimization, ISO/IEC 13818-2, power consumption, speeding-up, inverse discrete cosine transform-IDCT, variable length decoding-VLD, Huffman coding, embedded system Abstract: In this paper, we have proposed optimized real-time MPEG-2 video decoder. The decoder has been implemented in one FPGA device as a HW/SW partitioned system. We made timing/power-consumption analysis.and optimization of the MPEG-2 decoder. On the basis of the achieved results, we decided for hardware implementation of the IDCT and VLD algorithms. Remaining parts were realized in software with 32-bit RISC processor. MPEG-2 decoder (RISC processor, IDCT core, VLD core) has been described in high-level Verilog/VHDL hardware description language and implemented in Virtex 1600E FPGA. Finally, the decoder has been tested on the Flextronics prototyping board. Strojno in programsko razdeljena optimizacija in FPGA implementacija MPEG-2 video dekoderja Ključne besede: MPEG-2 video dekoder, FPGA implementacija, optimizacija, ISO/IEC 13818-2, poraba moči, pohitritev, inverzna diskretna kosinusna transformacija-DCT, dekodiranje s spremenljivo dolžino-VLD, Huffmanovo kodiranje, vgrajeni sistem Izvleček: V članku smo predstavili optimiziran MPEG-2 video dekoder namenjen dekodiranju v realnem času. Dekoder smo realizirali v enem FPGA vezju kot kombinacijo programske in strojne rešitve. Opravili smo analizo in optimizacijo hitrosti delovanja ter porabe moči MPEG-2 dekoderja. Na podlagi rezultatov smo se odločili, da časovno in energijsko zahtevne algoritme (inverzna kosinusna transformacija ter dekodiranje s spremenljivo dolžino) realiziramo direktno v strojni opremi, ostale dele dekoderja pa realiziramo z RISC mikroprocesorjem. Celoten MPEG-2 dekoder (RISC procesor, IDCT jedro, VLD jedro) smo opisali v visokonivojskih jezikih Verilog in VHDL in ga implementirali v Virtex 1600 programirljivem FPGA vezju. Vezje dekoderja smo nato preizkusili v realnem testnem okolju na FPGA prototipnem sistemu proizvajalca Flextronics. 1. Introduction MPEG-2 video standard is an important standard for video compression today/1/. MPEG-2 coding/decoding algorithm can be found in different applications such as digital video broadcast, DVD, cable TV, graphics/image processing cards, set top boxes, digital cameras, SDTVand HDTV. Due to different profiles and levels of the MPEG-2 video standard, every application has specific ratio between performance and quality. Since modern multimedia applications increase both aspects of the MPEG-2 compression, it is necessary to achieve best performance in terms of real-time operation and reduced hardware cost. The MPEG-2 standard includes several compression techniques such as variable length coding (VLC), discrete cosine transform (DCT), quantization and motion compensation. It was shown that some of these parts can be optimized with parallel structures and efficiently implemented in the hardware-software partitioned system. Recently, several MPEG-2 decoders have been developed either as software based applications /2/ or hardware based ASIC custom chips /3/. A parallel decoder for the MPEG-2 standard implemented on a shared memory multiprocessor was presented in /2/. The primary goal of this approach was to provide an all- software memory solution for real-time high quality video decoding and to investigate the important properties as they pertain to multiprocessor systems. In /3/, a VLSI chip for real-time decoding of MPEG-2 video was developed as hardware based ASIC device with un-optimized decoding functions. In literature, we haven't found any description of combined hardware-software implementation of the MPEG-2 decoder on a single chip. The reason is probably the lack of technology that provides efficient hardware/software implementation. With the recent advantages in technology from leading manufactures of the programmable devices (Xilinx-Mi-croblaze /4/, Altera-Nios /5/), the proposed design gain importance. The VLC decoding algorithm and IDCT algorithm are implemented with fast parallel architectures directly in hardware. Hardware part is described in VHDL/ Verilog and implemented together with the RISC processor in a single Virtex 1600E FPGA device. Decoding of the coded bitstream, inverse quantization, motion-compensation are running in software on 32-bit RISC processor which is implemented in FPGA and uses Linux as the operating system. This is so due to the non-existence of efficient parallel architectures for these algorithms. This partitioning was selected in order to achieve better timing properties and lower power consumption. 86 M. Verderber, A. Zemva: HW/SW Partitioned Optimization and VLSI-FPGA Implementation of the MPEG-2 Video Decoder Informacije MIDEM 33(2003)2, str. 86-91 With the proposed parallel optimization in hardware, up to 40% improvement is achieved compared to the complete software implementation. The main benefit of our MPEG-2 decoder is leveraging best characteristics from hardware and software based solutions. The proposed MPEG-2 video decoder was tested on the Flextronics FPGA based industrial board /6,7/ which serves as a testing environment and forms the intermediate step In VLSI chip design cycle. This paper Is organized as follows: the next section describes timing optimization and optimization of the power consumption of the decoder. The implementation of the MPEG-2 decoder is presented in Section 3. Finally, Section 4 completes the paper with a conclusion and future work. 2. Optimization of the MPEG2 Video Decoder As illustrated in Figure 1, coded pictures are first variable length (Huffman) decoded and theirtype Is determined from the header information. Pictures are inverse scanned and inverse quantized. Inverse quantization is performed in two steps. Data are first divided with a quantization-step matrix and then scaled with a scale factor. sion than I or P pictures. The ISO/IEC 13818-2 (MPEG-2 video part) standard defines only the frame for different algorithms included in the standard /8/. Therefore, there are various possibilities to optimize particular parts of the decoder. In order to deal with timing and power-consumption optimization, we have developed a software support in visual C++ programming language. A Screenshot of the software tool is shown in Figure 2. - ■ s ssâ S wtsstumH «F m nernm tttis »erorn mmîâtïwîî ftwàsé merlus tiwrx SB.Ktaaro I&C! liftwjiîhç tiwrs ïi ■«■»• Dt.fi «ccmtitrç rtra; CftPtftAnB» HF TttE riwçs WF * I •>' rtvefsgp ffiUnlzet tf*e« Ut» »«Mi™ tWWS >,W« t$.84«> ¡¡«i»l 9'WI»! VarUblf I.ifljlth tali»» I, tovcr« $03:1 \_/\_/ Codedsequences(I.B,B.P) f \-mif* UW Mvirsvy s. / !f:Vf;ty Motu« (haiüiv OCT «lien [kïafcl ¡iRirks Figure 1 : Structure of the ISO/IEC 13818-2 MPEG-2 video decoder MPEG-2 standard defines 3 types of the coded frames (I, P, B pictures). Intra-coded pictures I take advantages of the picture's spatial correlation. They do not reference any other pictures in the coded bit stream. They provide fast random access with only moderate compression. I pictures are only DCT decoded while no motion compensation Is performed. Inter-coded pictures P, B consider also temporal correlation between successive pictures (motion compensation). P pictures are decoded using motion-compensated prediction from the past I or P pictures which are stored in the Frame-Store-Memory. The compression for P pictures Is better than for I pictures, and P pictures can be used as reference points for additional motion compensation. Bldlrectionally predicted pictures B provide the highest degree of compression. They are decoded using motion-compensated prediction from either past and/or future I or P pictures. Since B pictures are not used in the prediction of other B or P pictures, such pictures accommodate more distortion and hence yielding more compres- Figure 2: Program for MPEG-2 software simulation This software allows us to simulate input sequences with different settings (profile/level, bit-rate, l/P frame distance, number of frames in GOP, frame/field pictures and all other coder/decoder parameters). The complete analysis can be performed and timing properties of particular algorithms included in the standard can be simulated. For timing analysis, elapsed time of the decoding parts in mill-seconds is measured for every decoded sequence. Finally, the speed of the program execution is evaluated. Based on the obtained results, we have estimated equivalent decoding speed for real-time decoding. 2.1. Timing Optimization Figure 3 shows a computational load of the decoding functions in MPEG-2 decoder. Color transformation and display 17% Bit stream header parsing 1% Motion compensation 36% £ \ Huffman decoding and inverse quantization 21% Inverse DCT 25% Figure 3: Computational power distribution for MPEG-2 decoding 87 Informacije MIDEM 33(2003)2, str. 86-91 M. Verderber, A. Zemva: HW/SW Partitioned Optimization and VLSI-FPGA Implementation of the MPEG-2 Video Decoder The data in the Figure 3 are based on simulations of source input format (SIF) (352x244, 25Hz) resolution pictures coded at 4 Mbits/s containing two B-pictures for every P-picture. As illustrated in Figure 3, the most computational expensive parts of the decoder are motion compensation, inverse DCT and VLD decoding. For variable length decoder (VLD), a lookup table based decoder structure proposed by Lei and Sun /11 / has been used. It is one of the fastest known variable length decoders today /1 /. It decodes each codeword in a single cycle regardless of its length. The block diagram of the Lei-Sun VLD is illustrated in Figure 5. The main idea of our decoder is to exploit advantages of the parallel structures which can be efficiently implemented in hardware. Hardware implementation of DCT and VLD decoder promises better results compared to software based algorithms. The key point of a parallel hardware structure is reduced number of operation and an ability to work in parallel. On the contrary, hardware implementation of motion compensation does not gain performance versus software based solution. In our decoder, we have therefore built fast hardware cores for IDCT and VLD decoder. The basic computation element in a DCT-based system is the transformation of an NxN image block from the spatial domain to the DCT domain and vice versa. For the image compression standards, N is usually 8. From a hardware or software implementation point of view, an 8x8 block size does not impose significant memory requirements. Furthermore, the computational complexity of an 8x8 DCT is manageable on most computing platforms. Mathematical formulation for the 2D discrete cosine transform is shown in (1). F (u,v) = ^ }^f(x,y) cos I v |cos| .1=0 >■=<) I 16 1 CU,CV= -j= (m, v = 0)... otherwise 1 x,y coordinates in pixel domain(Q...l) u,v coordinates in DCT domain(0...1) (1) The separable nature of the 2D DCT is exploited by performing the 1D DCT on the eight rows and then the 1D DCT on the eight columns /9/. Several fast algorithms are available for calculation of the 8-point 1D DCT. In our decoder, scaled version of Chen has been used /10/. It was selected due to the minimum required number of additions and multiplication. Structure of Chen DCT is illustrated in Figure 4. FÜ w E2. F6 Fl, ES. Fil 7*\ Ü.5 \ 2f0 .............t X-I £ ► s \\ 0.5 H #/ 20 ■m 20 _2f4 JL = *4 __l_ 1 X /7 \\\ >1 i V n c ! < « \ \ A f ~ -v-t- 0.5 // •! // X w A...2Î7 i Data Input ! 'Upper Reg. | | Lower R.eg.UL°ad- Barrel Shifter N-i Codeword Sum ! ( ;im -nii I Adder ; 1......*.......*...... Figure 4: Modified Chen 1D inverse DCT structure j Codeword ; Decoded | C?ode-leugth j L I Table : vvord Table i Table t i AND-Plaiie i OR-Plane j OR-Plane i < 200 °C > 150 °C > 150 °C 4.1 Definicije pomembnejših parametrov feritnih materialov Normalizirane izgube v feritnem materialu Magnetne izgube so vsota histereznih izgub, izgub zaradi vrtinčnih tokov in preostalih ali remanenčnih izgub. Histerezne izgube so pri majhnih magnetnih gostotah v feritnem materialu zanemarljive. Izgube zaradi vrtinčnih tokov naraščajo s hitrostjo spreminjanja smeri tokov. Pri nizkih frekvencah so zanemarljive. Induktivni senzorji uporabljajo majhne magnetne gostote in višje frekvence magnetnih polj. Normalizirane izgube tanS/n.,. so neodvisne od velikosti jedra in zračne reže pri magnetno odprtih jedrih. Določajo ga le izgube zaradi vrtinčnih tokov in preostale izgube v feritnem materialu, zato ne vključuje histereznih izgub. Faktor narašča s frekvenco. Normalizirane Izgube v feritnem materialu merimo z računalniško podprtim merilnim sistemom. Merilni vzorec je toroidnojedroT 22 14 07, na katerega navijemo 20 ovojev dvakrat lakirane bakrene žice premera 0,25 mm. Merilno frekvenco za nizkoizgubne materiale spreminjamo med 10 kHz in 1 MHz. Merilni sistem pri sobni temperaturi 23 ± 2 °C zagotavlja stalno gostoto 0,1 mT v feritnem jedru, izmeri induktivnost tuljave ter njeno enosmerno in efektivno upornost. Na osnovi izmerjenih parametrov izračuna normalizirane izgube feritnega materiala po enačbi (4.1): v tan 8 2 - iz ■ f ■ L tan 8£ (4.1) l-t; Ve 97 Informacije MIDEM 33(2003)2, str. 96-99 L. Knez: Induktivni senzorji pri čemer je Ref efektivna upornost tuljave, navite na feritno jedro, pri frekvenci 100 kHz ali 1 MHz in vključuje enosmerne in celotne izgube izražene v O., R0 je čista enosmerna upornost tuljave v Q.,f je merilna frekvenca v Hz, L induktivnost tuljave v H, ¡m začetna permeabilnost toroida in fie efektivna permeabilnost jedra z režo. Efektivna permeabilnost je vedno nižja od začetne. Podajamo jo za jedra z zračno režo. Izgubni faktorje za obe permeabilnosti enak, ker se pri jedrih z režo zmanjša tudi kot 8e. 4.2 Curiejeva temperatura Curiejeva temperatura Tc je temperaturna meja, nad katero izgubi feritni material svoje magnetne lastnosti. Začetna permeabilnost feritnega materiala ¡1-, sedaj pade na vrednost 1. 4.3 Temperaturni koeficient permeabilnosti Temperaturni koeficient permeabilnosti materiala ap je določen kot sprememba začetne permeabilnosti materiala zaradi spremembe temperature in ga podaja enačba (4.2). To je materialna konstanta, ki je neodvisna od reže. Ta faktor posledično vpliva na spremembo induktivnosti tuljave, če se spremeni temperatura v feritnem materialu. V enačbi nastopa relativna permeabilnost ¡a, ki je brezdimenzijska. Temperaturni koeficient permeabilnosti ar podaja enačba (4.2): a. - M-il V-n-V-n-fc-TA J_ K (4.2) pri čemer je fin permeabilnost pri temperaturi Ti in /Ui2 permeabilnost pri temperaturi T2 v stopinjah Kelvina. 5 Oblike in velikosti feritnih lončkov za induktivne senzorje Iz feritnih materialov 10G, 16G in 26G se izdeluje lončaste oblike feritnih jeder, ki so primerni za induktivne senzorje. Črka pri oznaki običajno pomeni lonček, številka pa njegov zunanji premer. 6 Izračun induktivnosti tuljave za senzor induktivnosti Izračunavanje induktivnosti tuljav z odprtimi magnetnimi krogi je težavno. Za praktične izračune pa enačba (6.1) določa dober rezultat /2/. Natančne vrednosti parametrov induktivnega senzorja ugotavljamo z meritvami. Induktivnost tuljave je določena s številom ovojev in njeno geometrijsko obliko. Vpliv feritnega materiala na induktivnost je izražena s koeficientom k. L = k• % 2 - D2 -N2 l- D D2 1 + 0,45---0,003 • / /2 [nH] (6.1) D = notranji premer tuljave v cm I = dolžina tuljave v cm N = število ovojev tuljave k = koeficient (k = 1 za zračno tuljavo, k = 3 za tuljavo s feritnim jedrom) Induktivnost po enačbi (6.1) lahko računamo, kadar je razmerje notranjega premera tuljave proti dolžini tuljave med 0 in 30. Kakovost tuljave Q podaja naslednja enačba: CD -L 2-71 ■ f ■ L Q = - R R (6.2) pri čemer je L induktivnost tuljave v H in R enosmerna upornost v Q in f frekvenca v Hz. Kakovost tuljave linearno raste s frekvenco dokler ne začne s frekvenco rasti še njena upornost. Kakovost nihajnega kroga pa se spreminja po značilni zvonasti krivulji. Iz znane induktivnosti in enosmerne upornosti lahko izračunamo kakovost tuljave pri različnih frekvencah. Recipročna vrednost kakovosti je izgubni faktor tuljave. 6.1 Zgled za izračun induktivnosti tipičnega induktivnega senzorja D = 0,72 cm / = 0,17 cm N = 300 ovojev k = 1 za zrak oziroma 2 ali 3 za feritni material Uporabimo enačbo (6.1) in izračunamo induktivnost zračne tuljave: L 1 -Tt2 -0,722 -3002 0,17 0 72 0 722 1 + 0,45 • ziLz. - 0,003 ' 0,17 ' 0,17" : 949 725,87 nH = 949,7 \lH Z upoštevanjem koeficienta k in enačbe (6.1) izračunamo še induktivnost tuljave s feritnim lončkom: L(k = 3)= 3 • 949,7 |iH = 2.849,1 \lH 98 L. Knez: Induktivni senzorji Informacije MIDEM 33(2003)2, str.96-99 6.2 Praktične meritve induktivnega senzorja Tabela 2. Praktične meritve induktivnega senzorja Frekvenca Induktivnost, kakovost Brez feritnega lončka S feritnim lončkom 10G S feritnim lončkom 26G 10 kHz L = 930 nH Q=3 L = 2.88 mH Q= 9,2 L = 2.87 mH Q= 9.2 100 kHz L = 931 fiH Q = 27.5 L = 2.89 mH Q = 73 L = 2.89 ml-I Q = 72 8 Literatura /1/ Dieter Nührmann, Professionelle Schaltungstechnik, 3. Auflage, Teil 3, Optoelektronik, Fernsteuerschaltungen, Steuer- und Regeltechnik, točka 7.8, stran 137, 138, ISBN 3-7723-6713-5, Franzis' - Verlag, 1992 /2/ George Rose, Große Elektronik-Formel-sammlung, 19. Auflage, ISBN 3-7723-5339-8, Franzis' - Verlag, 1995, stran 130 Induktivnost tuljave s feritnim jedrom se poveča za približno trikrat. Podobno je s kakovostjo Q, na katero najbolj vpliva vrsta feritnega materiala. Praktični rezultati se dovolj dobro ujemajo z izračunom. 7 Sklep Induktivni senzorji so zelo uporabni za nekontaktna stikala v avtomatiki. So robustni in skoraj neobčutljivi za umazanijo in okolje. Imajo dolgo trajnostno dobo. Delujejo lahko v širokem frekvenčnem področju. Zaradi robustnosti in zanesljivosti lahko sklepamo, da bo njihova uporaba še dolgo nepogrešljiva v industrijski avtomatizaciji in profesionalni elektroniki. Električne izgube in kakovost induktivnih senzorjev določa izbrani feritni material. Računanje parametrov tuljav z odprtimi magnetnimi krogi je lahko le približno. Mag. Leopold Knez, univ. dipl. inž., tel. (01) 5833 114, E-pošta: leopold.knez@iskra-feriti.si Iskra Feriti, d. o. o. Stegne 29, SI-1521 Ljubljana tel. +386 1 5833 114 faks +386 1 5833 235 Prispelo (Arrived): 06.06.2002 Sprejeto (Accepted): 25.05.2003 99 UDK621.3:(53+54+621 +66), ISSN0352-9045 Informacije MIDEM 33(2003)2, Ljubljana HOME AUTOMATION ON THE MOVE 1 Andrej Sostaric, 1 Bojan Imperl, 2 Boro Jerabek 1 HERMES SoftLab d.d., Ljubljana, Slovenia 2 Gorenje d.d., Velenje, Slovenia Key words; home automation, X.10, SMS, mobility, value added services, kitchen center Abstract: In this article we would like to show how an arbitrary home and building electronic system based on the home automation standards such as X10 might be addressed and controlled by an appropriate mobile technology. Urge for mobility of users, which may be at the same time either the inhabitants of these homes or even administrators and supporters, is growing. The possibility to control and observe the status of home appliances while being on the move away from home using our mobile phones is becoming reality today. As an example we will introduce the prototype system, which gained a lot of attention on the last INFOS conference and was made functional throughout the cooperation of two Slovenian companies, Gorenje and HERMES SoftLab. While Gorenje developed a so-called kitchen center, an unique all-in-one home appliance controlled by the personal computer, HERMES SoftLab contributed the X10 PLC protocol environment and HERMES SoftLab's Smart Service Mediator (SSM) platform, well known from the mobile operators' world, which enable mobile users to control their automated home remotely using ordinary mobile phones and short messaging system (SMS). When developed, this prototype system presented one of the world's first attempts to Integrate the home automation system with the GSM network using the SMS. Hišna avtomatizacija na pohodu Ključne besede: hišna avtomatizacija, X.10, SMS, mobilnost, storitve z dodano vrednostjo, kuhinjski center Izvleček: V članku bi radi pokazali, kako lahko nek poljuben dom in stavbni elektronski sistem, ki temelji na standardih hišne avtomatizacije kot je X10, usmerjamo in nadzorujemo s pomočjo primerne mobilne tehnologije. Potreba po mobilnosti uporabnikov, ki so lahko hkrati prebivalci teh domov ali celo administratorji in vzdrževalci, vedno bolj narašča. Možnost upravljanja in opazovanja statusa hišnih naprav s pomočjo mobilnega telefona med uporabnikovo odsotnostjo z doma postaja dandanes stvarnost. Kot primer bomo predstavili prototip takšnega sistema, ki je na zadnji konferenci INFOS požel veliko zanimanja in sta ga v sodelovanju razvili dve slovenski podjetji, Gorenje in HERMES SoftLab. Medtem ko je Gorenje razvilo takoimenovan kuhinjski center, edinstveno, vse-v-enem hišno napravo, ki jo nadzoruje osebni računalnik, je HERMES SoftLab prispeval strojno rešitev, temelječo na standardu X10, in sporočilno platformo Smart Service Mediator (SSM), dobro znano v svetu mobilnih operaterjev. Vse to omogoča mobilnim uporabnikom nadziranje avtomatiziranega doma na daljavo z uporabo navadnega mobilnega telefona in pošiljanja kratkih sporočil (SMS). Ob razvoju je ta prototip predstavljal enega prvih poskusov integracije sistema hišne avtomatizacije z omrežjem GSM, ki temelji na pošiljanju kratkih sporočil. Home automation In recent years there have been several attempts worldwide to develop a home and building electronic system (HBES) based on the Power Line Carrier (PLC) technology. The PLC technology uses existing electrical power lines in home and buildings to send the control signals for controlling various home appliances. However the different system specifications have confused planning engineers, contractors, installers as well as resellers, end-users, building owners and investors. This situation is hindering market acceptance and growth. Consequently each system lacks the necessary volume success. In Europe specifically there are three solutions, which are candidates to become the home and building electronic system standard: BatiBUS - represented by BatiBUS Club International (BCI) EIB (European Installation Bus) - represented by European Installation Bus Association (EIBA) EHS (European Home Systems) - represented by European Home Systems Association (EHSA) The three above mentioned associations have agreed to provide the technical basis for the convergence of these three systems so that in future there will be only one common system supported by relevant industrial companies. A common Association resulting from the amalgamation of BCI, EIBA and EHSA will promote the KNX standard. In the USA and in the last few years also in Europe another system, X10, gained high popularity due to its simplicity, low price, and adoption by the manufacturers. X10 is a PLC protocol that allows compatible devices throughout the home to communicate with each other via the existing 110/220V electrical power lines. Using X10 it is possible to control lights and virtually any other electrical device or collect the data from the sensors (temperature, humidity, motion etc.) from anywhere in the house with no additional wiring. X10 Power Line Carrier Protocol TheXIO PLC protocol /1/ defines the procedure for communication between the transmitting device and receiving device by sending and receiving signals over the power line wiring. These signals represent short RF bursts, a 120 100 A. Sostaric, B. Imperl, B. Jerabek: Home Automation on the Move Informacije MIDEM 33(2003)2, str. 100-104 kHz-coded signal superimposed on the 60Hz/50Hz electrical power line, with encoded digital information. TheX-10 signals are synchronized to the zero-crossing point of the AC power line - they are transmitted within 200 ms of the zero crossing point. Power line interfaces provide 50Hz square wave with a max. delay of 100 |js from the zero crossing point to the AC power line. The maximum delay between signal envelope input and 120 kHz output bursts is 50 |js. A binary 1 is represented by a 1 ms burst of 120 kHz, at the zero crossing point. If burst is not presented in this period, a binary 0 is assumed. These 1 millisecond bursts are transmitted three times to cover the zero crossing points of all three phases in a three phase power distribution system, as shown in Figure 1. V; 120 kHz _ 3.33 ms „ , 6.66 ms „ 10.0 ms 50 Hz Figure 1: The Power Line Cycle and theX10 signals. One cycle of the 50Hz power line carries one bit of information. In X10, transmission of the complete information consists of a sequence of three groups of bits (codes): start code, house code, and a number or function code (see Figure 2). START CODE HOUSE CODE NUMBER/FUNCTION CODE 10 10 10 0 1 Figure 2: The X10 coding scheme. The start code is a standard code denoting the start of the transmission and is transmitted within the first 2 power line cycles. The house code is a 4-bit code (any code from 0000 to 1111) and serves as the address of the target device to which the transmission is addressed. The number/ function code is a 5-bit code (any code from 00000 to 11111). Transmission of the house code takes 4 power line cycles, while the transmission of the number/function code takes 5 power line cycles. The house codes and the number/function codes are transmitted in a true compliment form on alternate half cycles of the power line - if a binary 1 is transmitted on one half cycle (1 millisecond burst of signal) then binary 0 (no signal) should be transmitted on the next cycle (See Figure 3). The Start Code is always 1110, which is a unique code and unlike the house and number/function codes does not follow true complimentary relationship on alternate half cycles. The start code is transmitted within 2 power line cycles (see Figure 2). The complete transmission (start code, house code, and a number/function code) hence requires 11 power line cycles and is always repeated twice with 3 power line cycles between each transmission: transmission of start, house, and number code followed by the transmission of the start, house, and function code. The house, number, and function codes are listed in Table 1. House codes A 0110 B 1110 C 0010 D 1010 E 0 0 0 1 F 1001 G 0101 H 1101 I 0111 J 1111 K 0011 L 1011 M 00 0 0 N 1000 0 0100 P 1 100 9 10 11 12 13 14 15 16 01100 11100 00100 10100 000 1 0 10010 01010 11010 01110 11110 00110 10110 000 00 1 000 0 01000 11000 Function codes All units OFF 0 0 0 0 1 All Lights ON 00 0 1 1 ON 00101 OFF 00111 Dim 01001 Bright 01011 All Lights OFF 01101 Extended Code 01111 Hail Request 1 0 0 0 1 Hail Acknowledge 10011 Pre-Set Dim 101X1 Extended Data 11001 Status=0N 11011 Status=OFF 11101 Status Request 11111 Table 1: The list of available house, number, and function codes. We can connect a large number of X10 receiving devices to the power line. To each of them we can assign one of 16 available house codes and one of 16 available number codes giving 256 different possible combinations. The X10 PLC home automation network consists of the following types of X20 devices: Receiving devices (executing the commands, no feedback information): light switches, receptacles, chimes Transmitting devices (transmitting signals to the power line: phone and PC controllers) Transceiver devices (receiving data and report status): motion detectors, flood detectors, thermometers X10 PLC Network devices: passive couplers, coupler repeaters, surge protectors, noise filters, and signal blocks that are installed in or near the electrical service panel. Such devices are necessary for providing consistent and reliable signaling performance, especially in the densely populated areas. 101 Informacije MIDEM 33(2003)2, str. 100-104 A. Šoštarič, B. Imperl, B. Jerabek: Home Automation on the Move Kitchen center of Gorenje Gorenje's kitchen center (Figure 3) is designed to become not only the central automation/information point of the kitchen but also the central point of the whole home. From outside it looks like a very modern and futuristically shaped kitchen-range. However, many are surprised when instead of a standard button-like control panel a modern flat panel touch screen silently rolls-out from the center whenever we want to monitor or control the system. By pressing the images on the touch screen we are able to turn on/off the oven or heating plates, control their temperature, start different cooking programs, set timers etc. The brains of the kitchen center represent a personal computer hidden in the very bottom of the center and transparent from the user's point of view. Internal electronic devices (heating plates, oven) are controlled by a proprietary controller maid by engineers from Gorenje, which is connected to the computer's serial port /2/. Another serial port is used for a X10 PLC modem, which connects the computer to the home's power line. This subsystem enables controlling of the X10 compliant home devices from the same point. The prototype system includes several light dimmers and switches as well as IR motion detectors. In general we could control also many other devices, such as heating and air-conditioning system, automatic doors, video and sound devices etc. /3/ Figure 3: Kitchen center of Gorenje Mobile phone as a remote control device To have a complete control over the wide variety of home devices is at least a nice feature. But wouldn't it be nice if we turned on the air-conditioning system when we were still on our way home? Or we could even use our mobile phone to open the garage door remotely. Some suggestions would perhaps bring a smile to the reader while some others are definitely attracting much more attention. For instance, wouldn't it be very useful if we got an alarm in shape of a short message (SMS) or a voice call in case that motion or fire detectors register some problems? There are several proprietary and closed systems, which provide exactly those functionalities, but there are as many different standards as there are solutions. At the same time, the cost of several isolated and non-compliant solutions exceeds the cost of the solution we are about to introduce. Today, almost everybody has a mobile phone. The penetration in some countries is reaching numbers higher than 70% of the whole population /4/. Mobile phone is not only voice-based communication device but is also becoming a payment instrument, electronic wallet, gaming device, and of course a special type of a remote controller. On the other hand, engineers from HERMES SoftLab developed a messaging platform, of which main task is to connect a mobile user with information resources and applications anywhere on the Internet. Starting from the fact that Gorenje's kitchen center is controlled by a built-in personal computer, it seemed a logical step to connect that computerto the Internet and enable users to remotely control the home automation system. But nonetheless, on the way to the final solution several problems were encountered, such as authentication and authorization issues, real-time message routing, security etc., which are successfully addressed and solved by the messaging platform. Smart Service Mediator platform SSM is a multi-channel platform that connects mobile users with the web servers using different communication channels /5/. While primarily it is being used for communication with short messages, voice, WAP, and HTTP channels are supported as well. Besides short messages, voice interaction is becoming more and more used, but in that case the cost of solution is higher because voice recognition system and text-to-speech synthesis must be involved. Basically, there are two different types of SSM installations, depending on the usage model. SSM platform may be installed either at the mobile operator (Figure 4) or in home servers /6/. In the first case, home servers must be connected to the mobile operator's infrastructure via Internet, while in the second case an in-house GSM modem is needed. Both installation types have their advantages and disadvantages depending on cost, business models, Internet availability etc. First option is cheaper for the end user and is promoted by the mobile operator. Second option is operator independent, needs no Internet connection but is less 102 A. Sostaric, B. Imperl, B. Jerabek: Home Automation on the Move Informacije MIDEM 33(2003)2, str. 100-104 suitable for the individual use because of the higher complexity at the user's side. Anyway, the solution with the GSM modem might be appropriate for larger enterprises. In the prototype version web server was connected to the mobile operator's (Mobitel) SSM platform over the Internet. Smart Service Mediator Home/Web Server Operator's HM| SMS-C Ijl User Database, CRM, Data Warehousing, and other operator's legacy system Prepaid/postpaid Figure 4: SSM platform as a part of mobile operator's service network. SSM platform communicates with the external world using standard communication and security protocols, such as XML for message coding, HTTP and HTTPS for transport and message encryption. In Figure 4, reader can notice also a connection between the SSM and mobile operator's billing systems - SSM is used also as an additional revenue generator because it handles and counts the messages traveling through the system. To these messages we can attach service data records (SDR) meaning that users would pay more than just a cost of short messages for this extra service. Following is a communication scenario between a mobile user and home automation system while remotely turning on the heating device: Heating sys em "Turn on heating" "Access denied" "Heating on" "Turn on healing" O Routing and access checking "Access denied" Decoding and command mapping "Heating on" Exection and status generation "Heating on* 1. User initiates the action by sending an SMS with the predefined content structure (i.e. "Turn on heating" or "Heating on") to the certain number or to the so- 3. 4. called large account1 (i.e. 1010). The message reaches the SMS Center (SMS-C), which is a vital part of the mobile operator's infrastructure and takes care of all in/outcoming SMS messages. SMS-C forwards the message to the SSM. SSM performs two main tasks - it routes the messages to the relevant home web server depending on a LA number and performs the authorization checks. SSM enables an easy user grouping and generation of access check lists. Only authorized users are allowed to control the devices in a certain home automation environment. If the access is granted (step 2a) the message is routed to the destination web server determined by the URL specified in the SSM settings. Otherwise, user gets a message containing denial of a service (step 2 b). Web server parses the message sent by a mobile user. If the message is valid appropriate action is taken - in our case, an X10 command is sent via X10 PLC modem to the heating system with the aim to turn it on. Heating system performs the action and returns the status, which is then forwarded back to the user. The example shown above is only about turning on the heating system in a house. For controlling the kitchen center devices, such as oven, heaters, fan, and some other household devices, such as lights, alarm and dimmers, the following syntax is used: command device arg where command ON, OFF, STATUS, HELP (abbreviations allowed: ON, OFF, S, H) device ALARM/1..m/, LIGHT/1..n/, OVEN, (abbreviations allowed: A, L, O, S) arg If command = ALARM, arg can vary between SILENT and LOUD (set by default) If command = LIGHT, arg can vary between 1 to 10 (default is 10). Arguments from 1 to 9 dim the light (if lights are actually attached to dimmer X.10 devices). Arguments 0 and 10 have the meaning of turning the lights ON/OFF. Following are some examples used in connection with the kitchen center: ON L1 30 (dim lightl to 30%) ALARM2 ON (turn on the second alarm in the house) OWEN OFF (switch the oven off) STATUS OWEN (get the oven status) etc. 1 Large accounts (LA) or large account numbers are short mobile numbers, usually up to 4 digits long, which are used for easier dialing/addressing of mobile data services. 103 Informacije MIDEM 33(2003)2, str. 100-104 A. Šoštarič, B. Imperl, B. Jerabek: Home Automation on the Move All examples from above were used in a so-called pull mode, where users send messages and trigger some activities or status reports. However, SSM enables also push functionality, where messages can be sent to mobile users without their requests in case some special situation occurs - i.e. user can be notified with a short message triggered by the motion detector. Motion detectors are not the only originators of pushed messages. You can imagine some other devices, such as fire/smoke/water detectors, timers etc. Conclusion Mobile phones have definitely marked current generations in the same way radios, TV sets and cars did in the past. They have become a necessity alowing users of mobile phones to be constantly in contact with each other and in contact with information. The work described in the paper presents a step further - it alows users of mobile phones to be constantly in contact also with a number of different devices either at home or at work. Eventhough the integration of home appliances with the mobile network may seem an insignificant task, it requires a deep knowledge of a number of different technologies and tight cooperation of partners from a different areas. In this case, two inovative companies, HERMES SoftLab - a software engineering company, and Gorenje - a manufacturer of home appliances, have joined their effort and brought ideas to life. Integration of home appliances with the mobile network opens a variety of possibilities both in the business and in consumer environments and the full potential of the features it brings is yet to be discovered. References /1 / B. Berner, C Elliott. Approaching Home Automation, Smart Home Systems, 2001 /2/ B. Jerabek, Z. Cencen, U. Sonjak, Kuhinjski center prihodnosti, Gorenje, Velenje, November 2000. /3/ A. Šoštarič, SMS - fun or something more?, Telelnfos conference, Ljubljana, May 2001. /4/ The Demand for Mobile Value-Added Services, Mobile phone penetration, Gartners report, February 2002. /5/ Smart Service Mediator (SSM) White Paper, HERMES SoftLab d.d., Maribor, July 2002. /6/ SMS Server (SSM Enterprise Edition) Administrators Guide, HERMES SoftLab d.d., Maribor, November 2001. Dr. Andrej Šoštarič, dipl. ing., Senior Project Manager and Teaching Assistant at University of Maribor HERMES SoftLab d.d., Litijska 51, 1000 Ljubljana, Slovenia Dr. Bojan Imperl, dipl. ing., Project Manager and Assistant Professor at University of Maribor HERMES SoftLab d.d., Litijska 51, 1000 Ljubljana, Slovenia Boro Jerabek, dipl. ing. Director of R & D Common Services Gorenje d.d., Partizanska 12, Velenje, Slovenia Prispelo (Arrived): 25.09.2002 Sprejeto (Accepted):25.05.2003 104 UDK621.3:(53+54+621 +66), ISSN0352-9045 Informacije MIDEM 33(2003)2, Ljubljana ABS-SENZORJI NA OSNOVI ALNiCO-MAGNETOV Franc Koplan Magneti Ljubljana, d.d., Ljubljana, Slovenija Ključne besede: magneti, trajni magnetni materiali, AINiCo-magneti, senzorji, sistem ABS (Anti - Lock Braking System ), ABS-senzorji, Hall-senzorji, magnetouporovni senzorji, zobnik, merjenje hitrosti vrtenja, magnetni pretok, oprema za kontroliranje in preskušanje Izvleček: Predstavljamo fizikalne osnove in princip delovanja ABS-sistema, zahteve za vgrajene AINiCo-magnete, ki so ključni element senzorja. Ilustriramo izdelavo samega ABS-senzorja, najpomembnejše značilne elektromagnetne lastnosti senzorja kot osnovo za nadaljnji razvoj elektronskega krmilnega modula ali alternativnih rešitev ter sprememb samega senzorja. Predstavljena je tudi možnost podjetja, da ponudi proizvode z večjo stopnjo integracije za nove potrebe trga ter izsledke razvojno raziskovalnega dela na področju razvoja opreme za kontroliranje in preskušanje magnetov za potrebe drugih področij raziskovalnega dela, proizvodnje elektronskih komponent ter izdelovanja magnetnih sistemov. ABS Sensor Applications Based on AINiCo Magnets Keywords: magnets, permanent magnetic materials, AINiCo magnets, sensors, Anti - Lock Braking System , ABS sensors, Hall sensors, magnetore-sistive sensors, gearwheel, rotational speed measurement, magnetic flux, measuring and control equipment Abstract: Organization Magneti Ljubljana presented the ABS - sensor application of its main production programme of AINiCo magnets and its potential for the production of the sensors. The article is intended both to domestic organizations for further joint technological development and to successfull producers, which already produce sensors, and are looking for a reliable and capable partner to supply them with parts with higher degree of integration. The company has over 50 years of tradition, is sucessful in the world market and has the quality management system certified according to most important standards, including the automotive specification ISO / TS 16949. According to its policy the company develops new production programmes, including new materials, magnetic systems and equipment for production and control of magnetic products and similar electronic components for the new demands and expectations of the market. The key sensors in the automotive applications and a scheme of the brake system of a vehicle are presented. The history, the benefits and the behaviour of the Anti-Lock Braking System are briefly described. The system usually contains 4 sensors and a common electronic unit, that handles the data from the sensors and controls the braking process, which is also appropriately described. It is emphasized, that organization Magneti Ljubljana produces magnets, which are the key element of the ABS sensors. The company has the basic knowledge for the manufacturing processes of ABS sensors. It has already in 1999 taken part In the tender for the production of sensors for its largest customer. The physical principles of the operation of the sensor, its construction and the behaviour of the induced voltage is described together with the typical requirements for used AINiCo magnets. The most important typical electromagnetic properties of the sensor are illustrated and this illustration enables further development of the electronic control unit as well as the development of the alternative solutions or modifications of the sensor itself. Some more contemporary and cheaper solutions for rotational speed measurements, offering important potential for further development and applications, were also mentioned and briefly described. Since the magnetic, dimensional and visual properties of the magnets in the sensor are critical, the quality assurance in the company obtains the 0-ppm level by 100% sorting processes. These processes are supported by specially developped electronic measuring systems enabling high productivity. The organization has developed its own high speed magnetizing and demagnetizing equipment, fluxmeters and equipment for visual control including optical measurement of dimensions and geometry. This equipment could be of interest also to organizations, which develop magnetic materials, assemble magnets and produce magnetic systems or other similar electronic components. 1 Uvod V prispevku želi podjetje Magneti Ljubljana, d.d. /1 / predstaviti uporabo in delovanje AINiCo-magnetov, vgrajenih v ABS-senzorje, ter svoje možnosti za proizvodnjo tovrstnih senzorjev. Članek je namenjen tako domačim podjetjem za morebiten skupen nadaljnji razvoj in nastop na svetovnem trgu kot tudi podjetjem, ki že proizvajajo senzorje in iščejo zanesljivega in sposobnega partnerja za dobavljanje sestavnih delov z višjo stopnjo integracije. Podjetje ima 50-letno tradicijo, v zadnjem desetletju ima nenehno in relativno visoko stopnjo rasti fizičnega obsega proizvodnje in se ponaša z zavidljivimi poslovnimi uspehi ter certifikati najzahtevnejših sistemov vodenja kakovosti avtomobilske industrije, z ISO / TS 16949 vred. Kupci so renomirani svetovni proizvajalci, predvsem s področja senzorskih aplikacij v avtomobilski industriji, pa tudi električnih merilnih instrumentov, elektromotorjev, tahogeneratorjev itd. Skladno s svojo poslovno politiko podjetje razvija nove programe, kamor spada poleg razvoja materialov in samih magnetov tudi razvoj magnetnih sistemov in procesne proizvodne opreme ter opreme za magnetenje, preskušanje, delno ali popolno razmagnetenje in kalibriranje magnetnih sistemov /5/. Raznovrstni trajni magneti so v avtomobilski industriji našli številna področja uporabe /4/, razvoj pa se še nadaljuje, še posebej v smeri nenehnega izboljševanja varnosti, za- 105 informacije MIDEM 33(2003)2, str. 105-109 F. Koplan: ABS-senzorji na osnovi ALNiCO-magnetov nesljivosti, ekonomičnosti in prijaznosti do uporabnika ter okolja. Ključni senzorji /2/ v avtomobilu so povezani s pozicijo (obese, pedal / plin, krmilje), hitrostjo gibanja vozila (ABS), temperaturo (notranja, regulacija klime, armatura, motor, prenos), hitrostjo gibajočih se delov (gredi, prenosi, avtomatska sklopka), z vibracijami in udarci (motor, varovanje pred požarom). Na sliki 1 so shematsko prikazani sklopi senzorjev v avtomobilu. Slika 1: Senzorski sklopi v avtomobilu /2/ Slika 2: Shema zavornega sistema avtomobila /3/ Na sliki 2 je shematsko prikazan zavorni sistem avtomobila /3/, ki ga sestavljajo: senzor hitrosti vrtenja koles (ABS-senzor), elektronska krmilna enota, hidravlična enota, senzor odklona od smeri, senzor krmilnega kota (volana), ak-tuatorji in zavorni diski / bobni. ABS je kratica za Anti - Lock Braking System, to je sistem, ki preprečuje blokiranje vrtenja koles med zaviranjem, s čimer zagotavlja večji zavorni učinek ter lažje vodenje vozila, povečano stabilnost vozila in ohranjanje varnostne razdalje. Navadno sistem sestavljajo skupno 4 senzorji na posameznih kolesih ter skupna elektronska enota, ki signale iz senzorjev obdela in vodi proces zaviranja. Elektronska enota pravilno deluje nad minimalno mejno hitrostjo, pri čemer z moduliranjem pritiska v zavorah, torej z zaviranjem in sproščanjem zavor, regulira zmanjševanje hitrosti vozila na ta način, da se hitrost kolesa obvladovano zmanjšuje, kolo pa se pri tem ne sme popolnoma zaustaviti, dokler je hitrost večja od mejne. V večini primerov se na ta način zagotovi najkrajša možna zavorna pot. Sistem ABS je bil razvit že leta 1930 za letala ter patentiran tudi za avtomobile. Zaradi izboljšanega vidika varnosti je pričel doživljati širšo uporabo v obdobju od 1975 do 1979, ko je bil v Združenih državah Amerike uveden v tovorna vozila. Leta 1980 so ga pričeli avtomobilski proizvajalci vgrajevati v osebna vozila, najprej v višji cenovni razred, z nadaljnjim razvojem in nižanjem stroškov pa je hitro našel svoje mesto tudi v avtomobilih nižjega cenovnega razreda. ABS-sistem s 4 senzorji deluje na naslednji način: Ko elektronski modul na osnovi signala iz senzorja prepozna, da bo kolo blokiralo, s tuljavo zapre ventil, ki je navadno odprt, ter s tem prepreči nadaljnje dovajanje hidravlične tekočine in nadaljnje zaviranje kolesa. Elektronski modul nadaljuje opazovanje signala iz senzorja iz tega kolesa. Če se kolo ustavlja hitreje kot druga tri kolesa, odpre tuljavo ventila. Ujeta tlačna razlika se izravna v rezervoarju glavnega cilindra. Ko kolo znova dobi hitrost, modul vrne tuljavo v normalno stanje, ki omogoča dotok tekočine. Podjetje Magneti Ljubljana, d.d. izdeluje AINiCo-magnete, ki so bistveni del ABS-senzorja, zato bo v nadaljevanju predstavljen samo tovrstni senzor, razpolaga pa tudi s ključnim znanjem za proizvajanje samih senzorjev. Tako je podjetje v letu 1999 že konkuriralo za kooperacijsko proizvodnjo nekaterih tipov senzorjev za svojega največjega kupca magnetov. 2 Senzor ABS z AINiCo-magnetom 2.1 Fizikalni princip delovanja Dajalni sistem sestavljata zobnik iz mehkomagnetnega materiala, ki se vrti skupaj s kolesom, in sam senzor, kjer se zaradi vrtenja zobnika spreminja magnetni pretok, kar ima za posledico inducirano napetost. V nadaljevanju bodo predstavljeni časovni poteki inducirane napetosti na senzorju, posneti pri laboratorijski postavitvi merilnega sistema, prikazani na sliki 3. SENZOR ZOBNIK Slika 3: Lega senzorja glede na zobnik /6/ 106 F. Koplan: ABS-senzorji na osnovi ALNiCO-magnetov informacije MIDEM 33(2003)2, str. 105-109 Merjenje hitrosti vrtfkjazobnika z itokabo senzorjana magnetni «sovi Slika 4: Spreminjanje magnetnega pretoka zaradi vrtenja zobnika ter potek inducirane napetosti /6/ 2.2 Izdelava senzorja Senzor sestavljajo: magnet polov nastavek spojni del za pritrditev polovega nastavka na magnet tuljavnik s kontakti tuljava priključni kabel z nosilcem, tesnili in mehansko zaščito. Ključni del senzorja je AINiCo-magnet valjaste oblike, ki je generator magnetnega polja. Po potrebi je ta magnet lahko tudi profilno brušen. Na sliki 5 je prikazan značilni magnet pred vgradnjo v senzor, na slikah 6 - 8 pa izdelan, nezalit senzor brez kabelskih povezav za priključitev na elektronsko enoto. K \' Slika 5: Liti AINiCo-magnet za ABS-senzor Slika 6: Zabrizgan magnet s polovim nastavkom in kontakti za priključitev na kabel Slika 7: Polov nastavek za koncentracijo silnic Slika 8: Izdelan, nezalit senzor s tuljavo Značilni podatki za magnete so podani v tabeli 1. Navadno je uporabljen liti material, ki daje pri enakem volumnu nekoliko boljše magnetne lastnosti, in razmerje med premerom in dolžino 1:3, kar postavi delovno točko magneta nekoliko nad področje maksimalnega energijskega produkta. Tabela 1: Najpomembnejše karakteristike AINiCo-magneta Karakteristika Značilna vrednost Premer valja od 4 do 10 mm Dolžina valja od 15 do 40 mm Remanenca Br - minimalno od 1100 do 1250 mT Koercitivnost BHC od 45 do 60 kA/m Maksimalni energijski produkt BHmax od 32 do 40 kJ/m3 Ker so magnetne lastnosti za pravilno delovanje senzorja kritične, v podjetju zagotavljamo zanje nivo 0 ppm s 100-odstotnim kontroliranjem in preskušanjem. Z ozirom na funkcijo ter način vgradnje so za magnet postavljene relativno visoke zahteve glede toleranc dimenzij in druge geometrije, videza, t.j. okrušitev in livarskih napak, pa tudi nivoja razmagnetenja. Za izpolnjevanje teh zahtev je bilo tre- 107 informacije MIDEM 33(2003)2, str. 105-109 F. Koplan: ABS-senzorji na osnovi ALNiCO-magnetov ba razviti visokoproduktivne elektronske merilne sisteme za magnetenje, merjenje magnetnega fluksa, razmagne-tenje, vizualno kontrolo ter nekontaktno kontrolo dimenzij in geometrije. Ta oprema je zanimiva tudi za organizacije, ki se ukvarjajo z razvojem magnetnih materialov, vgradnjo magnetov in izdelavo magnetnih sistemov ter podobnih elektronskih komponent in je bila razvita v okviru lastnega razvoja procesne ter merilne opreme oziroma v okvirih projektov izboljšav v tehnoloških procesih v sodelovanju z Ministrstvom za gospodarstvo /5/. Na sliki 9 je prikazan del naprave za elektromagnetno preskušanje magnetov za ABS-senzorje. Slika 9: Naprava za EM-preskušanje magnetov za ABS-senzorje Magnet mora biti čim bolj tesno povezan s polovim nastavkom iz mehkega železa, ki koncentrira silnice in s tem omogoča bolj izrazito spreminjanje magnetnega fluksa glede na razdaljo med vrhom polovega nastavka ter zobnikom. Konstrukcija in izdelava tuljave je tehnološko zahtevna in se izvaja po posebnem programu navijanja. Značilne karakteristike tuljave in izhodni signal senzorja so podane v tabeli 2: TABELA2 Karakteristika Tipične vrednosti Upornost od 0,5 do 2 kfl Induktivnost (1 kHz) od 500 do 1200 mH U, inducirana (tip. 400 r/min, reža 0,8 mm) od 0,5 do 4,5 V Glede na izhodno napetost imajo nekateri tipi senzorjev integrirane elektronske elemente za obdelavo inducirane napetosti, kar omogoča miniaturizacijo ter nižje skupne stroške izdelave senzorja, predvsem na račun cene vgrajenih magnetov. V laboratoriju smo izvedli simulacijo delovanja senzorja (915 r/min, 70 zob) in posneli časovni potek inducirane napetosti ob prehodnem pojavu trenutne zaustavitve zobnika (slika 10). mm\ -Mi ; 1 |U - p.' .'.ji " «v^wímtóíhn 1 »rtij i J. i.*, -iv4 • i ,• ' ^ ií ^ VOLT/D I V OFFSET Choo.2 < 50 . 00mV/d ¡ v K> . OOOV TIWK/DIV OELAY tZO.OOms/div -226. Oms Slika 10:Prehodni pojav ob zaustavitvi zobnika 3 Sodobni načini merjenja hitrosti vrtenja na osnovi integriranih vezij oz. senzorjev V zadnjem obdobju se v nižjem cenovnem razredu vse bolj uveljavljajo cenejše rešitve, temelječe predvsem na integriranih elektronskih elementih - Hallovih ter magnetou-porovnih senzorjih /6/. Tu lahko še vedno ostane pasivni dajalnik - mehkomagnetni zobnik (slika 11) ali pa zobnik nadomestimo z multipolno namagnetenim plastomagnet-nim aktivnim dajalnikom (slika 12). i.i.i.k ; ki i\ski si:n/.okji magni-i m.c;a poi.ja mi;r.ii;n.ii: hitrosti vrtkn.ia - pasivni dajai \ik Slika 11-.Sodobno merjenje hitrosti vrtenja s pasivnim dajalnikom in integriranim vezjem oz. magnetouporovnim senzorjem /6/ KI HKTRONSKI SI-N/ORJI \IAti\FTNI-XiA POl JA • AKTIVNI l).\MI.\IK -T -i—¡ ri J I L! L- . AiJ -X-. a A/ Slika 12:Sodobno merjenje hitrosti vrtenja z aktivnim dajalnikom in integriranim vezjem oz. magnetouporovnim senzorjem /6/ 108 F. Koplan: ABS-senzorji na osnovi ALNiCO-magnetov informacije MIDEM 33(2003)2, str. 105-109 Predvidevamo, dati novi proizvodi doslej uveljavljenih senzorjev z AINiCo-magneti tudi v naslednjem srednjeročnem obdobju večinoma še ne bodo nadomestili, zato vidimo v programu izdelave ABS-senzorjev z AINiCo-magneti novo priložnost za uspeh. Kupci namreč pri sebi instalirajo proizvode, temelječe na novih materialih, zmanjšujejo število svojih dobaviteljev oziroma celo prenašajo dele svojih proizvodnih programov k svojim ključnim dobaviteljem, da od njih prejmejo izdelke z višjo stopnjo integracije. /2. / L' Electricfil Industrie: Sensors to meet the challenges of productivity, Beynost, 1997 /3. / Bosch: Bosch braking systems, Tokyo, 2000 /4. / S. Kobe, P. McGulness: Application of permanent magnet materials, SLO-GER Meeting, Bled, 1998 /5. / F. Koplan: Računalniška podpora elektromagnetnemu preskušanju in vizualnemu sortiranju elektronskih komponent, Ljubljana, 2001 /6. / Philips Semiconductors: Data sheet - General rotational speed measurement, 1998 4 Sklep Predstavljena je bila fizikalna osnova delovanja, izgradnja senzorja na osnovi paličastih AINiCo- magnetov, značilne vrednosti njegovih najpomembnejših karakteristik za morebitno izdelavo elektronskega krmilnega modula ali alternativnih rešitev samega senzorja in možnost podjetja Magneti Ljubljana, d. d., da ponudi trgu proizvod z večjo stopnjo integracije ter si tako še naprej zagotovi poslovni uspeh na trgu. Franc Koplan, univ. dipl. inž. fizike in elektrotehnike Magneti Ljubljana, d. d. Stegne 37, SI-1000 Ljubljana, SLOVENIJA tel. 386(0)1 507 47 11 faks. 386(0)1 511 12 95 e-pošta: f.koplan.svk@magneti.si 5 Literatura /1./ Magneti Ljubljana, d.d., The world-wide supplier of permanent metallic magnets [elektronski vir]. Magneti Ljubljana, 2002 [citirano 28. maj 2002; 12:00:00], Dostopno na URL-naslovu: www.magneti.sl Prispelo (Arrived): 06.06.2002 Sprejeto (Accepted): 25.05.2003 109 UDK621.3:(53+54+621 +66), ISSN0352-9045 Informacije MIDEM 33(2003)2, Ljubljana A 12-BIT FLASH ADC Anton Pletersek University of Ljubljana, Faculty of Electrical Engineering, Slovenia Key words: digital-to-analog, converter, precision, accuracy, INL, DNL, linearity Abstract: A 12 bit, single step flash digital-to-analog converter (DAC) in 0.6um CMOS was realized on 1.5mm2 silicon area and has power consumption of 0.5mW at 5V supply. Converter architecture based on resistor-string having 2**N resistor taps and layout-efficient coding scheme. The system features a precision, fast settling, offset canceling operational amplifier and has 0.002% linearity. The conversion time is 4us. 12-bitni bliskovni DAC Ključne besede: digitalno-analogni, pretvornik, precizija, točnost, integralna nelinearnost, diferencialna nelinearnost Izvleček: Bliskovni digitalno-analogni pretvornik, izdelan v standardni 0.6um tehnologiji CMOS na površini silicija1.5mm2 , ima minimalno porabo 0.5mW. Arhitekturo pretvornika sestavlja uporovna veriga z napetostnimi odcepi in CMOS stikali, ki so krmiljena na način, ki optimizira porabo silicija. Doseženo linearnost pretvornika (0.002%) zagotavlja ustrezno povprečenje, ki minimizira gradient spreminjanja upornosti polisilicija po silicijevi rezini. Z ustrezno optimizacijo internih zaklasnitev je dosežena hitrost pretvorbe 4us. I. Introduction The paper will discuss the digital-to-analog converter having the fast conversion time of 4(is at worst-case process. Concept based on resistors matching which guarantee the linearity of monolithic DAC to be in the 9 to 10 bit range. Performances can be extended to more then 12 bits, using so called layout averaging technique, which includes proper interleaving of passive components. Technique will be described in detail later in this paper. The result of such a technique is desensitizing the DAC to doping, thermal and misalignment gradients. In present paper we will describe the layout efficient architecture of the 12 bit flash DAC with proposed algorithm to extend linearity to 0.003%. We will discuss the basic flash system, followed by section with detail description of the DAC converter blocks, DAC converter operational amplifier and the concept for offset compensation. The layout averaging and gradient-over-silicon analysis using Matlab and in final section the measurement and performances will be presented. capacitance loaded the sensitive - internal analog line. The resistance of the chain, the parasitic capacitance, switch resistance and internal - analog line (IVA) parasitic have influence on converter settling performances and therefore conversion time. RJ!**N IVA s_2*'N-l R_l II. Basic Flash DAC A single step flash DAC converter, based on resistive chain and digitally controlled switches are shown from Fig. 1. The input digital code is converted to switch-control signals. Only one switch is close at a time. Resistor-chain is supplied from constant, temperature and supply stable reference voltage. Ideally, here are only two current contacts - on bottom and on top of the chain where the voltage reference is connected. There are 2**N taps which are voltage contacts to switches and no current flows through them. The large number of switches with their parasitic grid Fig. 1 DAC12 basic architecture. It is therefore important to make the resistance small enough to speed up the conversion. Lower chain resistivity requires larger driving capability of the voltage reference. The optimum exists between switch resistance, chain resistance and capacitance. To reduce the number of switches, connected to the IVA, the so called tree-decoding scheme might be a solution. As we will show later in this paper, 110 A. Pleteršek: A 12-Bit Flash ADC Informacije MIDEM 33(2003)2, str. 110-114 the good compromise can be found between layout density and the settling performances. Using additional resistive parallelism, the equalizing of the settling performances over full scale can be achieved. III. Circuit Realization A. Layout efficient decoding The principle is shown from Fig. 2. The 12 input NOR gate is realized by 12 N-channel devices in serial. The P-chan-nel devices are omitted, the single PMOS current generator is used instead. There are 2**N current generators in the circuit, only one delivers current into system at a time. Overall required bias current is therefore single generator current which is in the range of 5uA for 12 bits converter. The complete decoding is optimized to fast controlled of the switch having on lALside the capacitive loading, including the operational amplifier input capacitance. The layout concept including four-bit intersection is in Fig. 2. Twenty metal lines (double metal process) passes the N-channel area. One kilo-bit block is organized as binary coded area from 1, 2, 4, and 8 bits sub-blocks inserted into 9-bit converter. Last - 10-th bit select between the two 9-bit converters. To get 12-bit converter, four such a 10-th stages are organized in proper way. Voltage reference was chosen to be 4.1V at 4.5V minimum supply. To minimize the parasitic, the switches are realized from negative reference side to be NMOS only, around mid-area switches are T-gates and on positive-reference side, switches are again single channel-PMOS only. B. Interleaving and layout averaging The principle of operation of presented DAC guarantee the monotonisity and therefore the analog output always increasing with increasing of the digital code. No matter how large is polyl resistivity gradient, It will mainly influence on integral non-linearity (INL) and can be expressed as a dif- R42 R41 R32 R31 R22 R2I RI2 Rll 12 Hil DAC Res. Chain Averaging Remisiers Fig. 3. Layout averaging. Dark dots represent the current-poly 1-metal 1 contacts. This scheme corresponds to "Iay2" curves on MatLab analysis figures. ference between actual analog value (VanaJ) and ideal one (Vanajdeal) on internal analog bus (IVA - Fig. 1) and is equal to: INL = V ANA i • V ANA ideal _ ^ref y* dRk 2n ' h R R is resistor-unit (ideal), dRk is difference from unit value, If we assume that all mismatch terms are zero over resistors chain, then the worst-case error will occur at the middle of the chain: > JV-l -fi' —j-1 ¡il, xSi '.•■»I -Si M r r. A- (CM I &¥B =31 --¡nr.- "—f tors—1j p3~ï -J i -, ■■■'. ■ -41 ■ -'i7 1 • Il , I. wJ£ 'i v.l I (¡■s y ïfi'.i ¡at =» ±$> ' jk$s 'i mh> ^ |sr-:J îrœ-= -oTTo iSST^ MSt^j B JB^.'ji :3s>-= ±rrz -±trz ±tt~z ±s-^ iWr^f xfiM-f itei-f JL J I i, si 3 i> JL J i h Fig. 2: Four - bit segment from 12 bit DAC 111 Informacije M1DEM 33(2003)2, str. 110-114 A. Pletersek: A 12-Bit Flash ADC i ml? ■ i j ru!8 g : * j mltj ml6 r ■ ■ T • - a S" of2 j ofi of4 ■ i -»ï : «*'„* i : • 1- ■:-![■ ; ■ IS- • - :........ • - :.........r- ' r-Jh- ! ■■•■"ih* ? i . * si go if • : ; • I > . > ■ *5 • * : . f. '3 . \ *»: . j. ? • ■ : »■•» - : - : : •„, • . : .,, : i ■! ,!' i ' ■ : ■ "ir; »-ji—- t-.-JL. --.JI-.I .............»M'i..........• * •«»; ; • "IJJ ; VBlliS; - • ; ;;-|r; s7 ■ - « ......;........*......................" " , Mi, ......- I n,10. Ni- mn. J I_max:+.30uA >10 +-30uA*26iohma<-8mV V/l converter via POLY 1 resistor (w=3um) \sss L VRÜ1-I :vje.:ï> m« » Fig. 4: Stable current generator for offset calibration. Binary weighted source and sink currents are generated from stable bandgap reference voltage. And the maximum value of INL is: INLmi% = V, rcf dK r It is evident that there is also an amplifier offset voltage contribution to INL. It contributes directly to INL. For high precision conversion, offset cancellation is a must (Fig. 4, Fig,5 and Fig. 6). Maximum negative mismatch dominates at all the resistors in the lower half of the chain and the maximum positive mismatch occurs in the upper half of the chain or vice-versa, depends on resistivity gradient. Fig. 8 shows the INL error over all 12 bit on digital input. Layout averaging principle uses additional parallel resistors to each sub-block of the DAC (Fig.3). The number of sub-blocks and the appropriate number of additional resistors define the possible layout mirroring and scrambling combinations. The different types of mismatches may occur randomly in X and Y direction on silicon. The sub-blocks mirroring and scrambling are therefore required in all directions (Fig. 8, Fig. 9, and Fig. 10). The number of sub-blocks is limited by the connectivity between sub-blocks and between the averaging resistors. The polyl -to-metal contact resistivity may vary from 2 Ohm to 20 Ohm, which could be more the one LSB unit resistor. Serial connections are required (metal 1 and metal2), but they need to be done in proper way (temperature coefficient of Al metal resistivity). These contacts conduct the all-resistors main-chain current and may cause the majority of INL and DNL error. OYR;OV tu-UV (40,120. IM~I00uA) Fig. 5: High gain class AB amplifier having input voltage range from negative rail to 300mV from positive rail. 112 A. Pleteršek: A 12-Bit Flash ADC Informacije MIDEM 33(2003)2, str. 110-114 OUTDA12 VBP s29 ■ ab28pn 266 3 u ! VA The layout - four bit intersection is shown from Fig. 7. b H □ b a vdda opaoyt opaiilil s28 vdd»fl • opaoul on . oB * of4 ■ sign_offs.* vsifajjfts ■ opainn sigofT oi'4 oi3 of2 on Fig. 6: Amplification of internally generated analog voltage Viva and offset correction circuitry. Next important layout constraint is mismatch minimization. The resistor-unit value and its width on layout influence on analog output delay and on mismatch between units. Huge mismatch occurs when equal units have different neighbors. IV. Conclusion The required matching of resistors in chain using so called end-point analysis is relatively high and is derived from INL expression: INL < 0.5LSB. J_ '2n fyomatching] N is converter precision. The 12 bit DAC require 0.025% resistors matching which is theoretical and practical possible limit when all available techniques are implemented. That means the layout is very critical part of the analog circuit design. Again, theoretically is possible to realize the active element matching. As a result, the mismatch and drift occur and the conversion accuracy may again be much lower then is converter precision. Our first measurements using code density principle and end-point approach without layout averaging give an encouraging result for INL, which was within +-2LSB at more then 50% samples. Layout averaging may improve the result for more then +-1.5LSB as is shown from Fig. 8 to Fig. 10. Much better result gives so called "best-fit" approach. Nevertheless, the proposed layout averaging, as is shown from Fig. 3 for 12 bit flash DA converter, is a challenge for designers to improve the result where fast conversion is of the most importance in integrated system on silicon. The principle itself guaranty the DNL performance to be much better then +-0.5LSB. b □ EW b m m b < e Ms ¡as B H ' m ' 1 ' E O B ¡ft B <»1 B d ; el q ; a Q B Q e b ! b Bl*| ET b br b la B B Q b veW EQ b b e OWP n i Q vs#a B B B Q V3S RE-'P CJ - B D 133 E> B a REFM Fig. 7: Four - bit segment from the layout, as is shown from schematic in Fig. 2. There are a number of different possible approaches like dual-ramp DAC /1/, where the accuracy depends on current generation accuracy, comparators offset and on clock frequency stability. Encouraging approach is a self-calibration method /2/, but it requires a long calibration period. It is clear that all improvements are possible mainly when using scaled down technologies which allows operation at much higher clock frequencies. Both principles may give conversion time better then 10us. 113 Informacije MIDEM 33(2003)2, str. 110-114 A. Pleteršek: A 12-Bit Flash ADC Kapaka upcmost) Napafca upornosti kvadratta t o Ï-0.5 0.5 £ o ?-0.5 I O V r t r •1000 ' -1000 ^ Vi""1) X {um] Napaka tftoh« rtupeiostl (lay. iay2 in !ay2rPH>) 1600 2000 2SC0 code [Isbj Pc'oiajl Lfcfw (lay n saySl 3-EOO 4C00 I C i- i r- I'2 Namaka izhxxîr^e napetosti (lay. t x [un) înlay^p) 1500 2000 25C0 codeflsCj Položaji uporov (lay >n Iay2) J . t. p»'* ♦ p2'y ♦ t p4Vy t p5'y? 0 0 001 0 0 0 •200 -100 o 1 -3 „pO , pr* . p2'y » pj'l* . (XVy . (¿V 0 0 0.005 -O 0 002 -O «32 Fig. 8: Three curves are as follows: -4LSB maximum INL at the middle of the string, mirroring-parallelism --1.5LSB and layout averaging 8:4 give accuracy of 1LSB. Gradient in Y direction is (0.5K-code-direction). Fig. 10: Random mismatch and random weighting as is shown on first and last canvas. In X direction are resistors string of 0.5k codes, in Y direction are 8 times 0,5k codes and parallel string. Napaka upornosti kvadratka Acknowledgment Author would like to thanks to Roman Benkovic for useful discussion and for mismatch analysis in MatLab. f », I 1 -2 3-a 500 -1000 .,000 -500 y[um] x |um) Napaka Izhodno napotosli (lay. !ay2 in Jay2rflip) 500 1000 1500 2000 2500 3000 3500 4000 codo [Isb] Položaji uporov (lay in lay?) This work was done in association with AMS AG, as a part of the complex analog-digital ASIC. References [1/ William D. Mack, M. Horowitz, R.A. Blauschlld, "A 14 Bit Dual-Ramp DAC tor Digital-Audio Systems", IEEE Journal of Solid-State Circuit, Vol. SC-17, No.6, Dec.1982, pp 1118-1126. /2/ D.W.J. Groeneveld, H.J. Schouwenaars, H.A.H.Termeer, C.A.A.Bastiaansen, "A Self-Calibration Technique for Monolithic High-Resolution D/A Converters", IEEE, Journal of Solid-State Circuit, VOL. 24, No.6, Deo. 1989, pp1517-1522. sqerr a = pO + pl'x + p2'y + p3'x2 + p4'x'y + pS'y3 0 0.0) 0.01 0 0 0 y lom) Anton Pleteršek Faculty of Electrical Engineering, Tržaška 25, 1000 Ljubljana, Slovenia e-mail:anton@kalvarija.fe.uni-lj.si Fig. 9: Linear gradient in X/Y direction gives four max. and four minimums. They correspond to the number of segments that alternate in direction X. Prispelo (Arrived): 06.06.2002 Sprejeto (Accepted): 25.05.2003 114 UDK621,3:(53+54+621 +66), ISSN0352-9045 Informacije MIDEM 33(2003)2, Ljubljana AUTOMATIC GAIN ADJUSTMENT IN CONTACTLESS COMMUNICATION SYSTEMS V. Kune, M. Atanasijevič Kunc Faculty of Electrical Engineering, University of Ljubljana, Ljubljana, Slovenia Key words: automatic gain control Abstract: Systems for contactless short range communications are more and more frequently used for different applications like access control, inventory and ticketing. Such systems comprise a RF transmitter emitting magnetic (electromagnetic) field and one or more transponders, which are supplied by the RF field. The transponder modulates the RF field to send information to the transmitter, which also comprises a reader system. The data transfer can be unidirectional (from transponder to reader) or bi-directional. The receiver system in the transmitter senses the modulation of RF field caused by transponder(s) on the transmitter antenna. Since the distance from transmitter antenna to transponder can vary from practically zero to the maximum operation range, the dynamic range of receive signals is very high. The gain of receive channel must be high to successfully detect the small receive signal but high gain can cause problems in case of large input signals. The solutions to the problem are the clipping of the input signal or automatic gain control or receive channel. The proposed solution describes an automatic gain control, which is specially adapted for RFID applications, as it successfully exploits the special nature of signals in such systems. Avtomatsko nastavljanje ojačenja v brezkontaktnih komunikacijskih sistemih Ključne besede: avtomatska nastavitev ojačenja Izvleček: Sistemi za brezkontakno komunikacijo skokovito pridobivajo na pomenu, saj njihova uporaba nezadržno narašča. Takšen sistem sestavlja oddajnik RF moči, ki oddaja elektromagnetno polje in eden ali več odzivnikov ki to polje uporabljajo za vir energije in preko modulacije RF polja pošiljajo podatke oddajniku. Pretok podatkov je lahko enosmeren, samo od odzivnika do oddajnika, ali pa v obe smeri. Za sprejem podatkov od odzivnikov vsebuje oddajnik RF moči tudi sprejemni kanal. Sprejemnik opazuje signal na oddajni anteni in ojači vsako spremembo nivoja oddajnega signala. Na ta način sprejemnik zazna modulacije RF polja s strani odzivnikov. Ker je razdalja med sprejemnikom In odzivnikom lahko zelo različna, od praktično nič pa do maksimalne razdalje, ki še omogoča komunikacijo, je razpon možnih nivojev sprejemnega signala zelo velik. Ker seveda želimo zanesljivo sprejemati tudi najmanjše vhodne signale, ima spremna stopnja veliko ojačenje, kar lahko povzroči probleme pri visokih nivojih vhodnih signalov. Da bi preprečil napačno delovanje v takšnih primerih imamo na razpolago dve možni rešitvi. To je omejevalnik signala ali pa avtomatsko prilagoditev ojačenja nivoju vhodnega signala. Članek opisuje posebno izvedbo sistema za avtomatsko nastavitev ojačenja, ki je prilagojena za sprejemnike signala brezkontaktnih odzivnikov in uspešno izkorišča posebnosti signalov v teh sistemih. 1. Introduction When designing an RFID receiver a maximum communication range is always one of major design goals. This implies that the receive gain is set as high as possible considering the input noise level. The result is that in case the transponder Is close to reader antenna and the Input signal level is much higherthan the minimum one, the signal at the end stages of receive channel exceeds the liner region of amplifier stage thus causing problems in data communication. Two possible solutions for this problem exist. The simplest possible solution is signal clamping. When the predefined level of the signal amplitude is reached the gain of the gain stage is decreased so that the amplitude can not increase further. This of cause causes signal distortion but since we are usually only interested in receiving digital data the distortion can be tolerated. A bigger disadvantage of clamping system becomes evident In case of communication where a significant level of disturbance signal Is added to the communication signal. The disturbance signals usually do not exceed the signal clipping level so they appear at the end of receive gain chain amplified with full gain of receive channel. On the other hand the communication signals are usually higherthan the clipping level so their amplitude is amplified with smaller gain. The obvious result Is that the ratio of communication signal to disturbance signal can significantly degrade at the end of receive gain chain compared to the input. The communication signal recognition is aggravated or in worst case becomes impossible. The second possibility is automatic gain adjustment of the receive channel where the receive gain is decreased in case of higher input signal levels. The gain than is the same for communication signal as well as for any possible disturbance signals resulting in no decrease of signal to disturbance ratio. 2. AGC system design Automatic gain control (AGC) circuits are well established in telecommunication and audio systems. The basic design problem in AGC design is the impact of gain change on 115 Informacije MIDEM 33(2003)2, str. 115-117 V. Kunc, M. Atanasijevic Kunc: Automatic Gain Adjustment in Contactless Comunication Systems the input signal. The input signal degradation due to AGC action must be kept at minimum and all important signal parameters (information content) should not be affected. To achieve this the nature of the input signal must be carefully studied and the AGC system designed for the particular input signals. The most important parameters are the gain change decision algorithm and the speed at which the gain is decreased and increased. The classical AGC solution comprises compactors which determine if the signal amplitude at given gain stage is lower or higher than the predefined level for AGC action. If that level is exceeded the AGC reacts by rapid gain decrease. This mode of operation is called attack mode and the speed of gain decrease attack speed. The AGC system remains in this attack mode till the gain decrease results in signal amplitude below the AGC threshold level. At that point the AGC system enters second mode called decay mode. During decay the gain starts increasing back towards it original (high) level. In case the signal amplitude again exceeds AGC threshold level as a result of decay action or input signal increase the AGC systems returns to attack mode. At constant signal level the AGC system constantly switches between attack and decay mode so the decay speed must be orders of magnitude lower than attack speed to minimise the impact of mode switching on the input signal. The AGC system action is finally finished when the input signal is low enough that the decay action restores the default high gain and the AGC system is deactivated. Our design solution of AGC system differs from above described classical one as it was designed for specific type of input signals existing in RFID communication. The protocol of RFID communication starts with the command sent from the reader to the transponder. The transponder reacts on the command and sends required data to the reader. The actual data is usually preceded by a preamble to prepare the reader for receiving the data. The coding format of the data is known so the AGC system has the information of the minimum and maximum possible time between two pulses. It is also reasonable to assume that the transponder is not able to change position in the RF field in the timeframe of data transfer so the same signal amplitude inside one data package can be expected. But immediately after the end of data transfer from one transponder a communication with different transponder, having completely different position in RF field and therefore different signal amplitude can start. It is evident that the AGC system for such signals must have a fast attack speed to set the gain correctly well inside the preamble before the actual data receive starts. The second imperative is that also decay speed must be relatively high since the reader must be prepared to receive new data at completely different signal level in a short time after the first data transfer is finished. To satisfy these requirements we devised an AGC system, which has three modes of operation instead of two as in classical solution. These modes are attack, decay and idle mode. The attack mode is started when the signal amplitude at the output of gain stage exceeds the defined threshold level. A rapid gain decrease is triggered and the signal amplitude is reduced below the threshold level. The conditions for attack mode are not preset anymore but the system does not enter usual decay mode. Instead the system waits in idle mode till conditions for decay or new attack are fulfilled. In idle mode the gain is not changing and is kept at the level defined by previous attack mode. The transition from idle mode to decay mode occurs if there are no incoming signals for a certain amount of time. The detection of data is performed using second comparator which has threshold level far below the AGC attack level (approximately one half of attack level) but still well above expected noise level. During data transfer package input pulses are always above idle mode comparator level. When the data transfer is finished these pulses stop and the idle mode comparator is not producing output pulses. If this condition persist longer than twice the maximum time space between two pulses as defined by data coding protocol the AGC system changes state from idle to decay. The decay is fast since the reader must be prepared for new data package from another transponder in relatively short time. The AGC action is finished when the gain is increased back to the default value. The typical data receiving sequence using such AGC system starts with the preamble send by the tag. During preamble the receive channel evaluates if the signal is too high and reduces the gain accordingly by setting the AGC system to attack mode. Well before the preamble transmission from transponder is finished is the receive channel AGC system already in idle mode. It stays in idle mode all through data transfer since input signal above idle mode threshold is always present. After the data transmission is finished the AGC stays in idle mode for a defined time and changes state to fast decay mode. A case of short data transfer from three different transponders having different signal levels is presented on fig. 1. In the upper canvas the output signal of the receive gain stage is shown. The receiving signal from the first transponder (shown in second canvas) was higher than the ACG limit presented as two straight lines on the same canvas. The attack mode is triggered. The flag presenting the attack mode is shown in canvas four. The attack is repeated every time the output signal exceeds the upper or lower limit. After two periods of incoming signal the gain is adjusted and the AGC system enters idle mode. Following pulses are received correctly with the gain set during attack time. The correctly received digitised signal is presented on the lowest canvas. After the receive signal stops the AGC system remains in idle for a time longer than two maximum receive signals periods. This is followed by a fast decay mode (the decay mode flag is presented on canvas three). Two more signal packages follow. The second one has higher amplitude than the first one so the AGC system must reduce the gain practically to the lowest possible. After the end of receive signal package another fast decay 116 V. Kune, M. Atanasijevič Kune: Automatic Gain Adjustment In Contactless Comunication Systems Informacije MIDEM 33(2003)2, str. 115-117 cycle follows. The receive system is again ready for new receive signal package (third one) which has a low signal amplitude so no AGC action is needed. 3. Conclusion The AGC system for contactless data communication system using RF powered transponders was designed based on the idea that only through a throughout knowledge of the nature of receive signal an optimum automatic gain control can be devised. The resulting system is perfectly suited for the task since it performs necessary gain adjustment only during the preamble of the incoming data package while there is absolutely no gain change during the actual data transfer. It also allows extremely fast gain recovery after the end of data transmission. All this ensures a reliable data receive in complete incoming signal amplitude range. Canvas 1: Analog output signal after the AGC gain stage Canvas 2: Analog input signal Canvas 3: Fast decay mode flag Canvas 4: Attack mode flag Canvas 5: Clock signal for gain change counters (active during attack and decay) V.Kunc, M.Atanasijevič Kune Faculty of Electrical Engineering Tržaška 25, 1000 Ljubljana, Slovenia E-mail: vinko@kalvarija.fe.uni-lj.si Canvas 6: Digitised receive signal Prispelo (Arrived): 06.06.2002 Sprejeto (Accepted): 25.05.2003 117 UDK621.3:(53+54+621 +66), ISSN0352-9045 Informacije MIDEM 33(2003)2, Ljubljana MICROSYSTEM FOR ELECTRICAL CURRENT SENSING Albin Pevec, Janez Trontelj University of Ljubljana, Faculty of Electrical Engineering, Ljubljana, Slovenia Key words; integrated sensors, Hall sensors, current measurement, microsystems Abstract: In this paper a method for measuring electrical currents with a magnetic microsystem Is presented. With the use of two coils, core and a magnetic microsystem closed loop system can be constructed to measure the electrical current through the primary coil. The magnetic field, generated by the primary coll current is sensed by the sensor in the air gap and amplified. This signal is used to generate a current through the secondary coil and therefore compensating the magnetic field in the air gap. Mikrosistem za merjenje električnega toka Ključne besede: integrirani senzorji, Hali senzorji, merjenje toka, mikrosistemi Izvleček: Članek predstavlja metodo merjenja toka z uporabo magnetnega mlkrosistema. Z uporabo dveh tuljav, jedra In magnetnega mikrosistema je možno sestaviti zaprtozančni sistem, ki meri tok skozi primarno navitje. Tok skozi primarno navitje ustvari magnetno polje v jedru, katerega zazna senzor v zračni reži. Ta signal ustvari tok skozi sekundarno navitje in s tem kompenzira magnetno polje v zračni reži. 1. Introduction 2. Closed loop system There are various methods to measure electrical current. The most common methods include the use of a shunt resistor, a transformer or a magnetic sensor. Resistive shunts operate by giving a voltage proportional to the current going through the resistor. This offers good accuracy and low offset, but does not provide electrical isolation and can have high thermal drift. Due to this nonisolated method the resistor or the electronics can be destroyed due to transients. Transformers can be used to electrically isolate the measurement system from the main system, but the main disadvantage of this method is that this only works for AC currents. To extend the operation to DC or low frequency currents, a DC magnetic field sensing element must be added to the system. This can be achieved by adding a magnetic field sensor into the transformer core, by which the DC magnetic field is measured. If the magnetic field sensor signal is combined with the AC signal the measurement range of such a microsystem is extended into the low frequency region. The signals from the magnetic sensor and from the coil are combined in such a way, that the field in the magnetic core is always zero. This combination is a closed loop system. In a closed loop current measuring system the sensor is placed in a compensating field which drives the field across the sensor to zero. The compensating field is generated by a secondary coil with N-turns. Therefore the current in the feedback (secondary) coil is proportional to the field from the primary current scaled by the turns ratio. Usually a shunt resistor is placed in series with the secondary coil to generate a voltage proportional to the measured current. The sensor is situated in the air gap. The magnetic sensor and the amplifying circuitry can be integrated on the same die, reducing the complexity of the wiring. The principle schematic of this closed loop system is shown on fig.2. Integrated microsystem Imeas Rshunt F Imeas Umeas Urrteas Shunt resistor measurement AC current transformer measurement Fig. 1: Methods of current measurement - direct and galvanically separated Isec Sensor Iprim Uout Fig. 2: Closed loop magnetic current sensing circuit 118 A. Pevec, J. Trontelj: Microsystem for Electrical Current Sensing Informacije MIDEM 33(2003)2, str. 118-121 The output voltage for a single turn primary coil can be calculated from the following equation: Uout = Rout ■ I sec = Rout ■ Iprim • — N The measured output voltage is dependent on the Rout shunt resistance and on the secondary coil N turn number. With these two parameters the measured secondary current can be scaled down to the values, deliverable by the integrated circuit. The advantages for the closed loop system are: closed loop allows for higher accuracy the sensor always operates around zero magnetic field strength closed loop systems have higher bandwidths fast responses galvanic separation of the measuring system 3. Integrated microsystem for magnetic field sensing To measure the magnetic field in the magnetic core gap a magnetic field sensor must be placed into the gap. Two types of sensors can be used: discrete sensors (for example magneto-resistive, Hall sensors) integrated sensors (integrated together with the processing and amplifying electronics) The only requirement for the sensor is that it fits into the magnetic core air gap. Both types of sensors (discrete and Integrated sensors) have been successfully used. The advantage of the integrated sensor system is the simpler wiring, due to the minimal on-chip wire length also the noise introduction is largely reduced. The disadvantage of the integrated version is the overall larger device, which must be fitted into the magnetic core gap. The emphasis in this article is on the closed loop system with an integrated magnetic sensor, although the discrete version is very similar in operation. A N-well Hall sensor array was used as the sensing element. The Hall sensors can be easily integrated in standard CMOS processes. The array is made from 12 Hall sensors, each biased with 1 mA. On the same die also the processing electronics and the current driving amplifiers are integrated. Figure 3. shows the block diagram of the presented integrated circuit, figure 4. the layout of the integrated circuit with the integrated Hall sensor array in the middle. The magnetic sensor signal processing is similar for the Hall sensors and for the magneto-resistive sensors. Both sensor signals need to be alternated for offset compensating reasons. The sensor signal is amplified and buffered to provide current capability. Magnetic sensing IC Fig. 3: Magnetic sensing integrated circuit block diagram in Id. dlid'^?idPPP|ti iftrll i *_i H i_ii_ii;. ■ . •==•(! Fig. 4: Integrated microsystem for closed loop measurement 4. Simulation and measurement results The magnetic core and the two coils have been modeled, enabling the SPICE simulation of the whole microsystem. With that the principle and the realization could be simulated. On fig 5. the step response (0 -> 25A) simulation is visible. The expected secondary coil current is 12.5mA (25A /N=2000). The simulated current is smaller due to the finite open loop gain of the amplifiers. On the secondary current the internal offset canceling circuitry settling is visible. This offset canceling is achieved by HF switching of the sensor signals. 121 informacije MIDEM 33(2003)2, str. 118-121 A. Pevec, J. Tronteij: Microsystem for Electrical Current Sensing [prim 0 5 10 15 20 25 Isec TZBbm 12.60m 12.55m ■ 12.50m . 12.45m ■ 12.40m J 12.35m i'.i'. C.'jy; ¿ta*»» L Fig. 5: Simulated 25A step response On the following simulation the response to a 20A pulses with a frequency of 250Hz is shown. The response to these pulses is a combination of the secondary coil (HF response) and the sensor signal (LF response). Primary current Coil induced current C0-! induced plus IC current voltage output I , I , I i I .1,1,1,1 The measured value is-32.27dB (at low frequencies) and shows good matching with the expected value. Fig. 7: Frequency dependency of the system The positioning of the two coils largely influences the performance of the system, the best results are achieved when the primary and the secondary coil are overlapped and physically near to the sensor. The frequency response of a non-optimal coil positioning can be seen on fig. 8, where the secondary coil was placed on the opposite side of the primary coil on the magnetic core. In this position the secondary coil induces less voltage and therefore the coil induced high frequency response is lower by almost 3dB. Fig. 6: Simulation of current pulses The measured frequency response shows a flat frequency characteristics overthe requested bandwidth. At lower frequencies the IC microsystem is the dominant contributor to the output signal, at higher frequencies the microsystem acts as a virtual ground and the signal comes from the current transformer. The frequency response is on fig.7. As can be seen, the frequency response shows variations below 0.6dB over the frequency range of up to 200kHz (the scale of the plot is 1 dB/div). This means, that the mismatch between the secondary coil (dominant at high frequencies) and the sensor signal (dominant at low frequencies) is less than 0.6dB. The measurement was made with a network analyzer and colls with a 5/2000 turn ratio. The primary current was measured on a 10£2 resistor, the secondary on a 100£2. The expected result can be calculated : Uout /sec- Rout 5-100Q Uin Iprim ■ Rin 2000-1012 -0.025: Fig. 8: Frequency dependency of the system with non-optimal coil position 5. Conclusion It was shown, that a magnetic field sensing microsystem in a closed loop configuration for measuring currents has -32.04dB many distinct advantages over other methods. It combines the fast response times of the transformer method with the DC accuracy of the shunt resistor method. The Hall 120 A. Pevec, J. Trontelj: Microsystem for Electrical Current Sensing Informacije MIDEM 33(2003)2, str. 118-121 magnetic sensor, processing electronics and the current amplifiers are all integrated on the same silicon die, creating an integrated microsystem. This die with the sensors is placed into the core air gap. With the use of the microsystem approach the interconnecting lines are largely shortened and therefore crosstalk and interference possibilities are reduced in comparison with the discrete sensor version. With an optimal positioning of the two coils on the magnetic core an matching error of 0.6dB between the low frequency sensor and the high frequency coil response can be achieved. 6. Literature /1/ J. Trontelj, A. Pevec, J. Trontelj ml.: " Contactless current measurement with integrated Hall elements" ; The proceedings of the MIDEM 1997 conference /2/ A. Pevec, J. Trontelj: "Microsystems with integrated capacitive, magnetic and optical sensors" Informacije MIDEM nr. 3-2002 /3/ W. Koon: "Current sensing for energy metering", Analog Devices, Application notes www.eetasia.com/ARTICLES/2002APR/ 2002APR08_AMD_DSP_EMS_TAC.PDF /4/ Honeywell: "Magnetic current sensing", Honeywell, Application notes http://www.ssec.honeywell.com/magnetlc/datasheets/ an209.pdf dr. Albin Pevec prof. dr. Janez Trontelj University of Ljubljana, Faculty of Electrical Engineering Tržaška 25, Ljubljana, Slovenia Tel: +386 (01) 4768337 Fax:+386 (01) 4264644 Email: albin @kalvarija. fe. uni-lj. si Email: janez. trontelj 1 @guest. arnes.si Prispelo (Arrived): 06.06.2002 Sprejeto (Accepted):25.05.2003 121 Informacije MIDEM 33(2003)2, Ljubljana Čestitka prof. dr. Mariji Kosec za priznanje Ambasador Republike Slovenije v znanosti za leto 2003 20. junija 2003 je Slovenija dobila tri nove Ambasadorje Republike Slovenije v znanosti: Prof. dr. Marijo Kosec, Prof. dr. Damijana Miklavčiča in akademika prof. dr. Jožeta Trontl-ja. O odličnosti nagrajencev pričajo uradne utemeljitve, dostopne na spletnih straneh http://www.mszs.si/slo/min-istrstvo/nagrade/ambasador/2003.asp. Svečani dogodek nas je še toliko bolj razveselil, saj je med nagrajenci prvič tudi članica društva MIDEM, prof, dr. Marija Kosec, ki jo vsi člani dobro poznamo. Ne samo zato, ker je predsednica društva, temveč zaradi njene izžarevajoče energije in zagnanosti. Prof. dr. Marija Kosec, izredna profesorica za materiale na Naravoslovnotehnični fakulteti, Univerze v Ljubljani, in vodja Odseka za elektronsko keramiko na Institutu „Jožef Štefan", je vodilna raziskovalka na področju elektronske keramike, pretežno feroelektrikov in piezoelektrikov. Med svetovne dosežke prištevajo rezultate njenih raziskav razumevanja sinteze sol-gel tankih plasti in prahov v sistemih Pb(Zr, TOO3. S tem je odprla nove možnosti nlzkotemperaturnih sintez (pri 400°C), kar je novost v svetu keramičnih materialov. Rdeča nit njenega dela je odličnost in mednarodno uveljavljanje Slovenije in slovenske znanosti. Rezultate raziskav je prof. Koščeva objavila v 95 člankih, večinoma v uglednih revijah na področju materialov. Imela je 25 vabljenih predavanj na konferencah in 20 vabljenih predavanj na univerzah in inštitutih. Bila je sourednica 11 zbornikov s konferenc. Ima tri domače patente in en evropski patent. Njena dela so citirana več kot 500-krat. Z več prispevki je sodelovala v monografiji z naslovom "Sol-gel science and technology", ki je letos izšla pri založbi Kluwer. Ena izmed njenih odlik je zagotovo sposobnost, da zna odlično povezovati osnovne raziskave z razvojnimi in uporabnimi. Prof. Marija Kosec je nosilka več kot 30 pogodb z industrijo, tako tujo kot domačo. O kvaliteti njenih raziskav pa govorijo tudi pogodbe s tujimi partnerji, kot je npr. razvoj prototipov iz feroelektrične keramike, ki omogočajo popolnoma nov način tiskanja (MAN Roland, Druckmachinen, Ausburg, Nemčija). Prof. Koščeva s svojo raziskovalno aktivnostjo skrbi za stalno promocijo slovenske znanosti v svetu. V to kategorijo spadajo v prvi vrsti mednarodni projekti (NATO, 5. OP, COST) v vrednosti več kot milijon EUR. Pomembna je njena mednarodna pedagoška aktivnost. Bila je gostujoča znanstvenica leta 1993, predavateljica v okviru letne šole „Feroelektrične tanke plasti" leta 1995 in gostujoča profesorica leta 2001 s serijo predavanj „On ceramic processing", na elitni šoli École Polytehnique Fedérale de Laussanne (EPFL) v Laboratoriju za keramiko, ki ga vodi prof. Neva Setter. Prof. Koščeva sodeluje kot mentorica za diplomska dela, magisterije in doktorate tako z Univerzo v Ljubljani, kot v komisijah za zagovor doktorskih del po svetu, npr. v prej omenjeni EPFL, na Tehnični univerzi Copenhagen (Danska), Univerzi Oolu (Finska) in Univerzi v Corku (Irska). Pod njenim vodstvom je bila skupina na Institutu »Jožef Štefan« imenovana za Marie Curie Training Site in si od Evropske unije pridobila naziv Centre of Excellence za naslednja štiri leta. Leta 1997 je uspešno organizirala mednarodno delavnico v okviru N.A.T.O., leta 2000 paje predsedovala organizacijskemu odboru svetovnega kongresa o elektrokeramiki »Electroceramics VII«. Prof. Koščeva je članica vrste odborov in komisij s področja keramike tako v Sloveniji kot tudi v svetu. Omeniti je treba njeno prestižno članstvo v IEEC Ferroelectric Committee, saj so v njem samo štirje člani iz Evrope. Je marljiva in prizadevna predsednica društva MIDEM, ki gaje že leta 1999 popeljala v ugledno mednarodno združenje IMPAS. Kar koli se v svetu zgodi na področju elektronske keramike, še posebej na področju feroelektrikov, ne mine brez prof. Koščeve; naj bo to nova knjiga, posvetovanje, letna šola, večji projekt v okviru Evropske skupnosti ali pa samo zagovor doktorske disertacije. 122 Informacije MIDEM 33(2003)2, Ljubljana Prof. Koščeva je z raziskovalnim delom dosegla neverjetno mednarodno odmevnost in z nastopanjem v mednarodnih znanstvenih krogih veliko prispevala k prepoznavnosti Slovenije v svetu in k povečanju njenega mednarodnega ugleda. Tudi društva MIDEM. V imenu članov društva MIDEM ji izrekam iskrene čestitke! Marko Topič Posvet o novih tehnologijah Symposium on new technologies Igor Pompe Zavod TC SEMTO, Stegne 25, 1000 Ljubljana, Slovenija, semto@guest.arnes.si Zavod TC SEMTO je organiziral posvet o novih tehnologijah v dveh delih: 3. 6. 2003 v prostorih Univerze v Ljubljani, Fakultete za elektrotehniko, in 20. 6. 2003 v prostorih Instituta "Jožef Stefan (IJS). Namen posveta je bil seznaniti člane TC SEMTO z novimi tehnologijami in dejavnostjo nekaterih raziskovalno-razvojnih laboratorijev in skupin. V nadaljevanju podajamo naslove in kratko vsebino prispevkov. Obširnejše bodo posamezni avtorji poročali v člankih, ki bodo objavljeni v revijah Materiali in tehnologije ali Informacije Midem. Zavod TC SEMTO has organized Symposium on New Technologies in two parts: on June 3, 2003 in the premises of Univerza v Ljubljani, Fakulteta za elektrotehniko and on June 20, 2003 at Jožef Stefan Institute in Ljubljana. The aim of the symposium was information of TC SEMTO members about new technologies and activities of some of the research laboratories and groups. The titles and abstracts of the lectures are published as follows. More details can be found in the articles that will be published in the reviews INFORMACIJE MIDEM and MATERIALI IN TEHNOLOGIJE. Prispevki: Prof. dr. Marija Kosec, Institut "Jožef Stefan": Keramične tehnologije, keramične plasti iz raztopin Predstavljene so bile razne keramične tehnologije. Podrobneje je bil predstavljen postopek pridobivanja keramičnih plasti iz raztopin. Dr. Peter Panjan, Institut "Jožef Štefan" : Razvoj keramičnih prevlek za zaščito orodij in strojnih delov Predstavljena je bila paleta raznih nekaj mikrometrov debelih keramičnih trdih prevlek na površini orodja za zaščito pred abrazijsko, adhezijsko in kemotermično obrabo. S temi prevlekami se trajnost orodij poveča. Predstavljeni so bili tudi tehnološki postopki za nanašanje prevlek. Dr. Uroš Cvelbar, Laboratorij za plazmo, Institut "Jožef Štefan": Aktivacija površin polimernih materialov s kisiko-vo plazmo Obravnavan je bil postopek aktivacije površin polimernih materialov s kisikovo plazmo, da se doseže boljša omočlji-vost površine (lepše in lažje tiskanje ali boljše tesnjenje pri zalivanju ohišij). Dr. Miran Mozetič, Laboratorij za plazmo, Institut "Jožef Štefan": Perspektive široke industrijske uporabe pla-zemskega čiščenja Prikazan je bil postopek čiščenja površin z vodikovo plazmo. Možno je doseči atomsko čiste površine. Postopek je ekološko prijazna alternativa mokremu kemijskemu postopku, vendar zahteva relativno drage plazemske reaktorje. Dr. Vojteh Leskovšek, Inštitut za kovinske materiale in tehnologije: Nitriranje v plazmi Obdelan je bil postopek nitriranja v plazmi, postopek ke-motermičnega modificiranja površin za utrjevanje strojnih delov in orodij, ki se jim s tem poveča trajno nihajna in upo-gibna trdnost, občutljivost jekla na zareze pa se zmanjša. Poveča se korozijska odpornost nizko in srednje legiranih jekel. Opisan je bil tehnološki proces. Parametri se prilagajajo kemični sestavi in predhodni toplotni obdelavi jekel. Nizke temperature nitriranja omogočijo, da jedro strojnega dela ali orodja tudi po nitriranju ohrani svoje prejšnje mehanske lastnosti. Doc. dr. Drago Resnik, doc. dr. Danilo Vrtačnik, prof. dr. Slavko Amon, Laboratorij za mikrosenzorske strukture, Fakulteta za elektrotehniko, Univerza v Ljubljani: Napredni načini mikroobdelave silicija za senzorske in aktua-torske mikrostrukture Prikazani so bili postopki obdelave silicija pri izdelavi silicijevih 3D-mikrostruktur, kjer se izkoriščajo poleg električnih tudi mehanske lastnosti silicija. Kombinacije novih mikro- 122 Informacije MIDEM 33(2003)2, Ljubljana elektronskih materialov in naprednih tehnologij omogočajo realizacijo precizne površinske in globinske mikroobdela-ve zahtevnih silicijevih mikrostruktur. Marija Zupan, univ. dipl. kem. tehnolog, IETP PT, Kranj: Pet korakov do spajkanja brez Pb Predavanje je obsegalo razloge za vpeljavo spajkanja brez Pb v elektronski industriji, časovni načrt in korake, ki so potrebni za vpeljavo te tehnologije v proizvodnjo. Predstavljeni so bili ustrezni materiali in oprema ter merila za njihov izbor ( plošče, zlitine spajk, prevleke itd..). Doc. dr. Roman Kamnik, prof. dr. Tadej Bajd, Laboratorij za robotiko, Fakulteta za elektrotehniko, Univerza v Ljubljani: Robotika v sodobnem svetu Podano je bilo stanje pri razvoju in uporabi robotike. Podani so bili osnovni pojmi iz robotike in osvetljeni vzroki za pospešen razvoj. Predstavljena je bila uporaba robotov v industrijskem okolju in delo Laboratorija za robotiko na Fakulteti za elektrotehniko v Ljubljani. Dr. Vladimir Jovan, TC ARI: Avtomatizacija v industriji Predstavljeno je bilo stanje avtomatizacije in informatizacije v slovenskih proizvodnih podjetjih. V nadaljevanju je avtor predstavil glavne razloge za vlaganja v avtomatizacijo in informatizacijo proizvodnje v slovenskih podjetjih, podal oceno rezultatov izvedenih projektov, izpostavil kritične aktivnosti teh projektov in opisal strategije njihovega izvajanja v slovenskih podjetjih. V drugem deluje predavatelj predstavil vrsto izvedbenih projektov avtomatizacije in informatizacije proizvodnje, ki sta jih izvedli dve skupini z Instituta "Jožef Štefan",in sicer Odsek za sisteme in vodenje ter Odsek za avtomatiko, biokibernetiko in robotiko. Ob koncu je bilo v kratkem predstavljeno delo Tehnološkega centra ARI (TC za avtomatizacijo, robotizacijo in informatizacijo proizvodnje). Dr. Slavko Dolinšek, Fakulteta za strojništvo, Univerza v Ljubljani in Regionalni tehnološki center Zasavje: Tehnologija DMLS (neposredno lasersko sintranje kovinskih prahov - od izdelave prototipnih orodij do hitre proizvodnje) Predstavljeno je bilo delo Regionalnega tehnološkega centra Zasavje (RTCZ) s poudarkom na neposrednem laserskem sintranju kovinskih prahov za hitro izdelavo orodij ali malih serij izdelkov zelo zahtevnih oblik. Predstavljene so bile možnosti izdelave delov in/ali orodij v RTCZ. Dr. Martin Bizjak, Iskra Stikala: Kontaktni materiali za nizkonapetostne stikalne aparate Obravnavani so bili kontaktni materiali za nizkonapetostne stikalne aparate v energetiki. Osnovni material je srebro, ki je lahko legirano s kovinami, lahko pa so srebru primešana zrnca ali vlakenca kovine ali kovinskih oksidov in grafita. Grafit je lahko primešan tudi v obliki drobnih palčk. Dodatki v srebru določajo lastnosti kotaktnega materiala. Franc Koplan, univ. dipl. inž., Magneti; Paul McGuiness, Institut "Jožef Štefan": Merjenje razmagnetilnih krivulj do 450 °C Predstavljeno je bilo delo, opravljeno v sodelovanju med IJS in podjetjem Magneti Ljubljana, katerega rezultat omogoča merjenje razmagnetilnih krivulj pri temperaturah me-rjencev do 450 °C . Nova tehnologija daje potencialnim uporabnikom konkurenčno prednost pri razvoju aplikacij z magneti pri visokih temperaturah. Dr. Vincenc Nemanič, Institut "Jožef Štefan": Novi nano-materiali - obetaven točkasti vir elektronov Predstavljeno je bilo delo na Odseku za tehnologijo površin in optoelektroniko iJS. Predstavljene so bile katode s hladno emisijo iz ogljikovih nanocenk in drugih, novih materialov (npr. iz molibden sulfida). Dr. Darko Makovec, Institut "Jožef Štefan": Priprava MnZn-feritov s hidrotermalno obdelavo oksidov Podana je bila informacija o delu skupine z IJS in iz Iskre Feriti pri razvoju nove tehnologije priprave MnZn-feritnih prahov, ki temelji na hidrotermalnih reakcijah med izhodnimi oksidi. S hidrotermalno obdelavo oksidov je možno pripraviti fin feritni prah podobne sestave kot pri klasični metodi kalcinacije in mletja. Nova metoda je predvsem energijsko ugodnejša, ker dobljenih prahov ni treba intenzivno mleti kot pri klasičnem postopku. Darko Belavič, univ. dipl. inž., Hipot: Debeloplastne tehnologije Predstavljene so bile novosti v tehnologijah izdelave debe-loplastnih vezij in izdelava LTCC-podlag . 122 Informacije MIDEM 33(2003)2, Ljubljana Informacije MIDEM Strokovna revija za mikroelektroniko, elektronske sestavine dele in materiale NAVODILA AVTORJEM Informacije MIDEM je znanstveno-strokovno-društvena publikacija Strokovnega društva za mikroelektroniko, elektronske sestavne dele in materiale - MIDEM. Revija objavlja prispevke s področja mikroelektronike, elektronskih sestavnih delov in materialov. Ob oddaji člankov morajo avtorji predlagati uredništvu razvrstitev dela v skladu s tipologijo za vodenje bibliografij v okviru sistema COBISS. Znanstveni in strokovni prispevki bodo recenzirani. Znanstveno-strokovni prispevki morajo biti pripravljeni na naslednji način: 1. Naslov dela, imena in priimki avtorjev brez titul, Imena Institucij in firm 2. Ključne besede in povzetek (največ 250 besed). 3. Naslov dela v angleščini. 4. Ključne besede v angleščini (Key words) in podaljšani povzetek (Extended Abstract) v anglešcčini, če je članek napisan v slovenščini 5. Uvod, glavni del, zaključek, zahvale, dodatki in literatura v skladu z IMRAD shemo (Introduction, Methods, Results And Discsussion). 6. Polna imena in priimki avtorjev s titulami, naslovi institucij in firm, v katerih so zaposleni ter tel./Fax/Email podatki. 7. Prispevki naj bodo oblikovani enostransko na A4 straneh v enem stolpcu z dvojnim razmikom, velikost črk namanj 12pt. Priporočena dolžina članka je 12-15 strani brez slik. Ostali prispevki, kot so poljudni cčlanki, aplikacijski članki, novice iz stroke, vesti iz delovnih organizacij, inštitutov in fakultet, obvestila o akcijah društva MIDEM in njegovih članov ter drugi prispevki so dobrodošli. Ostala splošna navodila 1. V članku je potrebno uporabljati SI sistem enot oz. v oklepaju navesti alternativne enote. 2. Risbe je potrebno izdelati ali iztiskati na belem papirju. Širina risb naj bo do 7.5 oz.15 cm. Vsaka risba, tabela ali fotografija naj ima številko in podnapis, ki označuje njeno vsebino. Risb, tabel in fotografij ni potrebno lepiti med tekst, ampak jih je potrebno ločeno priložiti članku. V tekstu je treba označiti mesto, kjer jih je potrebno vstaviti. 3. Delo je lahko napisano in bo objavljeno v slovenščini ali v angleščini. 4. Uredniški odbor ne bo sprejel strokovnih prispevkov, ki ne bodo poslani v dveh izvodih skupaj z elektronsko verzijo prispevka na disketi ali zgoščenki v formatih ASCII ali Word for Windows. Grafične datoteke naj bodo priložene ločeno In so lahko v formatu TIFF, EPS, JPEG, VMF ali GIF. 5. Avtorji so v celoti odgovorni za vsebino objavljenega sestavka. Rokopisov ne vračamo. Rokopise pošljite na spodnji naslov. Uredništvo Informacije MIDEM MIDEM pri MIKROIKS Stegne 11,1521 Ljubljana, Slovenia Email: Iztok.Sorli@guest.ames.si tel. (01) 5133 768, fax. (01) 5133 771 Informacije MIDEM Journal of Microelectronics, Electronic Components and Materials INSTRUCTIONS FOR AUTHORS Informacije MIDEM is a scientific-professional-social publication of Professional Society for Microelectronics, Electronic Components and Materials - MIDEM. In the Journal, scientific and professional contributions are published covering the field of microelectronics, electronic components and materials. Authors should suggest to the Editorial board the classification of their contribution such as : original scientific paper, review scientific paper, professional paper... Scientific and professional papers are subject to review. Each scientific contribution should include the following: 1. Title of the paper, authors' names, name of the institution/company. 2. Key Words (5-10 words) and Abstract (200-250 words), stating how the work advances state of the art in the field. 3. Introduction, main text, conclusion, acknowledgements, appendix and references following the IMRAD scheme (Introduction, Methods, Results And Discsussion). 4. Full authors' names, titles and complete company/institution address, including Tel./Fax/Email. 5. Manuscripts should be typed double-spaced on one side of A4 page format in font size 12pt. Recommended length of manuscript (figures not included) is 12-15 pages 6. Slovene authors writing in English language must submit title, key words and abstract also in Slovene language. 7. Authors writing in Slovene language must submit title, key words and extended abstract (500-700 words) also in English language. Other types of contributions such as popular papers, application papers, scientific news, news from companies, institutes and universities, reports on actions of MIDEM Society and its members as well as other relevant contributions, of appropriate length , are also welcome. General informations 1. Authors should use SI units and provide alternative units in parentheses wherever necessary. 2. Illustrations should be in black on white paper. Their width should be up to 7.5 or 15 cm. Each illustration, table or photograph should be numbered and with legend added. Illustrations, tables and photographs must not be included in the text but added separately. However, their position in the text should be clearly marked. 3. Contributions may be written and will be published in Slovene or English language. 4. Authors must send two hard copies of the complete contributon, together with all files on diskette or CD, in ASCII or Word for Windows format. Graphic files must be added separately and may be in TIFF, EPS, JPEG, VMF or GIF format. 5. Authors are fully responsible for the content of the paper. Contributions are to be sent to the address below. Uredništvo Informacije MIDEM MIDEM pri MIKROIKS Stegne 11, 1521 Ljubljana, Slovenia Email: lztok.Sorli@guest.ames.si tel.+386 1 5133 768, fax.+386 1 5133 771 1 25