# December 2006, Volume 15, Number 4

**S. K. Goudos**
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Calculation and Modeling of EMI from Integrated Circuits inside High-Speed Network Devices

This work presents a numerical approach to the modeling of Electromagnetic Interference (EMI) from the emissions of ICs and PCBs inside rectangular metallic enclosures of network devices. The ICs are modeled as small magnetic and electric dipoles. Their interaction with the enclosures is studied with the dyadic Green\'s functions. Several calculation examples of surface current density on the metallic walls are given due to dipoles parallel to all directions. A Probabilistic Model is created from magnetic probe measurements in various types of router devices. Monte Carlo simulation is applied in order to perform a worst-case analysis. The applications of the above approach in PCB design are discussed.

- COORAY, F. R., CRAWHALL, R., COSTACHE, G. I. Radiated fields from circuit components inside rectangular enclosures with apertures. Canadian Journal of Electrical and Computer Engineering. 1991, vol. 16, no. 4, p. 143-147.
- GOULETTE, R. R. The measurement of radiated emissions form integrated circuits. In Proceedings of the IEEE International EMC Symposium. Anaheim, (USA), 1992, p.340-345.
- TAI, C. T., ROZENFELD, P. Different representations of dyadic Green's functions for a rectangular cavity. IEEE Transactions on Microwave Theory and Techniques. 1976, vol. 24, no. 9, p. 597-601.
- CRAWHALL, R. EMI Potential of Multiple Sources within a Shielded Enclosure. Doctoral Thesis, University of Ottawa, Ottawa, 1993.
- GOUDOS, S. K., VAFIADIS, E., SAHALOS, J. N. Monte Carlo simulation for the prediction of the emission level from multiple sources inside shielded enclosures. IEEE Transactions on Electromagnetic Compatibility. 2002, vol. 44, no. 2, p. 291-308.
- GOUDOS S. K., SAMARAS, T., VAFIADIS E., SAHALOS, J. N. Numerical approaches for EMI reduction of ICs and PCBs inside metallic enclosures. In Proceedings of the IEEE International Symposium on Electromagnetic Compatibility. Istanbul (Turkey), 2003, p. 513-518.
- RUBINSTEIN, R. Y. Simulation and the Monte Carlo method. New York: John Wiley & Sons, 1981.
- PAPOULIS, A. Probability, Random Variables and Stochastic Processes. Second Edition. New York: McGraw-Hill Series in Electrical Engineering, 1984.

Keywords: Numerical techniques, Electromagnetic interference, Printed circuit board design, Monte Carlo simulation

**M. Valek, M. Leone**
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Estimation of Radiated Fields of Small Horizontal Submodules Based on a Lumped-Element Model

A novel approach to the estimation of radiated electric field of small horizontal submodules is presented. The principle idea is to describe the radiating submodule-on-motherboard structure with a lumped-element equivalent circuit which includes both the geometrical and the electrical parameters. The electromagnetic emission from the structure is approximated by the radiation characteristics of a Hertzian dipole driven by the antenna voltage resulting from the connector equivalent circuit. Therefore, no time consuming numerical field simulations are needed to evaluate the radiated electric field. Instead, a fast frequency circuit analysis with e.g. PSPICE is sufficient. Moreover, this modeling approach provides a clear insight concerning the influence of geometrical and electrical parameters with respect to radiated emissions. Finally, the computational solutions are compared with experimental results, demonstrating a good correspondence regarding engineering purposes.

- LI, K., TASSOUDIJ, A., POH, S. Y., TSUK, M., SHIN, R. T., KONG, J. A. FD-TD analysis of electromagnetic radiation from modules-on-backplane configurations. IEEE Transactions on Electromagnetic Compatibility. 1995, vol. 37, no 3, pp.326 - 332.
- LEONE, M., NAVRATIL, V. On the electromagnetic radiation of printed-circuit-board interconnections. IEEE Transactions on Electromagnetic Compatibility. 2005, vol. 47, no. 2, pp.219 - 226.
- VALEK, M., LEONE, M., SCHMIEDL, F. Analysis of the radiation behaviour of motherboard-subboard structures. In Proc. of the 6th International Symposium on Electromagnetic Compatibility and Electromagnetic Ecology. St.-Petersburg (Russia), 2005, pp.175-178.
- PAUL, C. R. Introduction to Electromagnetic Compatibility. New York: John Wiley & Sons, Inc., 1992.
- BALANIS, C. A. Antenna Theory. New York: John Wiley & Sons, Inc., 1997.
- VALEK, M., LEONE, M. Radiation model for small horizontal submodules. In Proceedings of the VII EMC Europe. Barcelona (Spain), 2006, pp.426-430.
- LANGE, K., LOCHERER, K.-H. Taschenbuch der Hochfrequenztechnik. Springer-Verlag, 1986.
- CONCEPT Home Page: www.tu-hamburg.de/~tebr

Keywords: EMI of submodules, radiated emissions, lumped-element model, connector equivalent circuit, PSPICE analysis

**J. Drinovsky, J. Svacina**
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Estimation of EMI Filter Performance for the \"Worst Case\" System

This paper deals with the performance problem of the EMC filters. The core of this problem in EMC filter is the uncertainty of impedances that are connected to the input and output of a filter. In addition, an estimation technique is presented that gives approximate insertion loss of the filter. The performance of this technique was tested on several filters and the data obtained were checked by insertion loss measurement. The heart of the matter is based on the L C equivalent circuits, which are described by Y parameters. The estimation gives pretty good results for the 0.1 Ω/100 Ω and vice-versa systems and also for other systems.

Also discussed are system configurations with the Δ (delta) and (Y) star topologies of terminating impedances which better approximate the real situation on the input and output terminals of filter.

- HABIGER, E. Elektromagnetische Vertraglichkeit. Huthig Buch Verlag, Heidelberg 1992. 200 pages. ISBN 3-7785-2092-X
- CSN CISPR 17: Methods of Measurement of the Suppression Characteristics of Passive Radio Interference Filters and Suppression Components. Czech Technical Standard. Czech Normalization institute. Prague November 2000 (in Czech)
- SVACINA, J., Electromagnetic Compatibility, Principles and Methods. Brno University of Technology 2001. "Join to European Union".Volume 2, 156 pages. IBSN 80-214-1873-7
- MALACK, J. A., ENGSTROM, J., R. RF Impedance of United States and European Power Lines. IEEE Transactions on Electromagnetic Compatibility. 1976, vol. EMC-18, no. 1, p 36-38.
- SVACINA, J., DRINOVSKY, J. Approximative Estimation of EMI Mains Filters Properties in the "Worst-Case" System Operation. Acta Electrotechnica et Informatica, 2005, vol. 5, num. 1, p. 13 17. ISSN 1335-8243
- SCHLICKE, H. M. Assuredly Effective Filters. IEEE Transactions on Electromagnetic Compatibility. 1976, vol. EMC-18, no. 3, p 106-110. ISSN 0018-9375
- Schaffner Holding AG, Switzerland. http://www.schaffner.com/
- Schurter AG, Switzerland. http://www.schurter.com/
- FILTANA, Ltd., EMI Filters for AC Voltage 250V/50Hz 811 Series (data sheet). Polna, Czech Republic
- ELFIS Ltd., Czech Republic. http://www.elfis.cz/

Keywords: EMI mains filter, insertion loss, impedance termination, supply network impedance, the worst-case EMC filter insertion loss

**M. Bittera, V. Smiesko, K. Kovac**
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Problem of Bundled Two-Wire Cable of Tested Equipment in Emission Measurement

Many factors that influence radiated emission measurement exist. Except of factors relative to measuring chain \"test site - antenna - receiver\" there are some factors caused by operating personnel like inappropriate configuration of tested equipment, etc. Tested equipments contain generally attached cables of different length; the longer ones shall be shortened by folding into a bundle. The aim of this paper is to analyze the behavior of such cables and its influence on results of radiated emission measurement.

- CISPR 16-2-3 Specification for radio disturbance and immunity measuring apparatus and methods - Part 2-3 Methods of measurement of disturbances and immunity - Radiated disturbance measurements. Ed.1.0, IEC, 2003.
- CISPR 22 Information technique equipments - Radio disturbance characteristics - Limit and methods of measurement. 5th ed. IEC, 2005.
- BITTERA, M., SMIESKO, V., KOVAC, K. Analysis of EUT cable at radiated emission measurement. In Proceeding of 1st International Conference Advances in Mechatronics AiM 2006. Trencin (Slovakia), 2006, p. 85 - 88.
- BINGEMAN, G. Transmission lines as antennas. RF Design. 2001, vol. 2, no.1. p. 74 - 82.
- CHRISTOPOULOS, C. The Transmission-Line Modeling Method: TLM. Wiley-IEEE Press, 1996.
- BALANIS, C.A. Antenna Theory - Analysis and Design. 2nd ed. John Wiley & Sons, 1997.
- McDONALD, K.T. A parallelogram loop antenna. http://puhep1.princeton.edu/~mcdonald/examples/loopantenna.pdf
- HARRINGTON, R.F. Field Computation by Moment Method. IEEE Press, 1993
- HARTANSKY, R., MAGA, D., SIROKY, P. Numerical modeling of moment method for antenna simulation. Computing - International Scientific Journal. 2003, vol. 2, no. 1, p. 88 - 91.
- http://www.feko.info
- BITTERA, M., HALLON, J., KOVAC, K., SZOLIK, I. Some factors influencing uncertainty of radiated emission measurement. In XIVth International Conference on Electromagnetic Disturbances EMD 2004. Vilnius (Lithuania), 2004, p. 161-164.

Keywords: Radiated emission measurement, bundled two-wire cable, method of moment

**J. Hallon, K. Kovac, I. Szolik**
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Geometrical Configuration of Cabling as Factor Influencing the Reproducibility of EMC Immunity Tests

The paper deals with analysis of the influence of geometrical configuration of device cabling upon voltages induced in cable interfaces. The analyzed properties are the cable height and the cable length for common mode disturbance, and the loop width for differential mode disturbance. The analysis is solved both by analytical calculation and by numerical simulation. Achieved results are compared mutually as well as with results obtained by measurements performed according to standardized procedures. Finally the analyzed parameters are ordered in correspondence of their importance for objectivity and reproducibility of immunity tests against electromagnetic field.

- PAUL, C. R. A SPICE model for multiconductor transmission lines excited by an incident electromagnetic field. IEEE Transactions on Electromagnetic Compatibility. 1994, vol. 36, no. 4, pp. 342 - 354.
- PAUL, C. R. Analysis of Multiconductor Transmission Lines. New York: Wiley Interscience, 1994.
- OMID, M., KAMI, Y., HAYAKAWA, M. Field coupling to nonuniform and uniform transmission lines. IEEE Transactions on Electromagnetic Compatibility. 1997, vol. 39, no. 3, pp. 201 - 211.
- HALLON, J., BITTERA, M., KOVAC, K., SZOLIK, I. Influence of cables position upon repeatability of induced voltages during EMC immunity tests of large systems. In Proceedings of the XVth International Conference on Electromagnetic Disturbances, EMD 2005. Bialystok (Poland), September 2005, pp. 3.3-1 - 3.3-4.
- SPADACINI, G., PIGNARI, S. A. A bulk current injection test conforming to statistical properties of radiation-induced effects. IEEE Transactions on Electromagnetic Compatibility. 2004, vol. 46, no. 3, pp. 446 - 458.
- ADAMS, J. W., CRUZ, J., MELQUIST, D. Comparison measurements of currents induced by radiation and injection. IEEE Transactions on Electromagnetic Compatibility. 1992, vol. 34, no. 3, pp. 360 -362.
- Low Cost DC-500 MHz, 92 dB Logarithmic Amplifier AD 8307. Datasheet, Analog Devices, Inc., www.analog.com, 2003.
- EN 61000-4-3 Electromagnetic compatibility (EMC) - Part 4-3: Testing and measurement techniques - Radiated, radio-frequency, electromagnetic field immunity test.
- BITTERA, M., HARTANSKY, R. Electromagnetic compatibility EM field measurement. In Proceedings of the 8th International Symposium on Mechatronics MECHATRONIKA 2005. Trencianske Teplice (Slovakia), May 2005, pp. 84 - 87.

Keywords: Electromagnetic compatibility, immunity testing, multiple transmission lines, influence of electromagnetic field, numerical EM simulation

**T. Korinek, P. Piksa, M. Mazanek**
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Wideband Measurement in a Small Shielded Box Using Equiangular Spiral Antennas

Small shielded boxes are nowadays widely used for measurement of EMS, EMI and sensitivity properties of different devices. This paper deals with an improvement of commercial small shielded box parameters for a measurement of sensitivity of small mobile devices in 650 MHz to 4 GHz frequency band. Optimization of shielded box parameters is obtained by an inner area modification. Suitable wideband equiangular spiral antenna was designed for this measurement. Parameters of antenna inside the box, such as gain, impedance, directivity etc. are discussed in the paper. Effects of antenna positions in the box for a transmission are shown and the best configuration of antennas placing for the transmission in the shielded box is chosen.

- http://www.tescom-lab.com
- MAZANEK, M., KLEPAL, M., PECHAC, P., POLIVKA, M., BARTIK, H. Anechoic and EMC chambers - modeling, design, testing. In Proceedings of the Millennium Conference on Antennas and Propagation. Noordwijk, European Space Agency, 2000, vol. 2, p. 156-160.
- MUSHIAKE, Y. Self-complementary antennas. IEEE Trans. Antennas Propagat. December 1992, vol. 34, p. 23-29.
- DYSON, J. D. The equiangular spiral antenna. IRE Trans. Antennas Propagat. April 1959, vol. 7, p. 181-187.
- RUMSEY, V. H. Frequency independent antennas. 1957 IRE National Convention Record. March 1957, p. 114-118.
- PIKSA, P., MAZANEK, M. A self-complementary 1.2 to 40 GHz spiral antenna with impedance matching. Radioengineering. September 2006, vol. 15, no. 3, p. 15-19. ISSN 1210-2512.
- http://www.zeland.com
- ZVANOVEC, S., HAZDRA, P., KORINEK, T., PECHAC, P., MAZANEK, M. Measurement of shielding effectiveness of small shielded enclosure. In Proceedings of the International Symposium on Electromagnetic Compatibility - EMC Europe 2006. Barcelona (Spain), 2006, p. 249-252.

Keywords: Shielded box, sensitivity, wideband measurement, equiangular spiral antenna, electromagnetic compatibility measurement

**V. Krcmar**
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Broadband Measuring of Shielding Covers

The novel method utilizing coupled lines for the dielectric property measurement of shielding covers of composite materials is described. Characteristics of coupled lines designed by two symmetrical strip lines with a common side wall, which is made of the tested material, are mentioned. It allows measuring the dielectric property in the frequency range up to 5 octaves. The circuit analyzer with a high dynamic range is used for parameters evaluation. The method was utilized at the research of the technology of abnormally shaped shielding covers of composite materials.

- UYSAL, S. Nonuniform Line Microstrip Directional Couplers and Filters. Boston: Artech House, 1993.
- http://www.turnkey.net/rftools.htm
- GUPTA, K. C., GARG, R., BAHL, I., BHARTIA, P. Microstrip Lines and Slotlines. 2nd Edition. Boston: Artech House, 1996.
- Operation manual, Vector Network Analyzer, Model 37347A.
- PAUL, R. C. Introduction to Electromagnetic Compatibility. New York: John Wiley, 1992.
- SCHEJBAL, V., BEZOUSEK, P., CERMAK, D., NEMEC, D., FISER, O., HAJEK, M. UWB propagation through walls. Radioengieering. 2006, vol. 15, no. 1, p. 17 - 24.
- HIPPEL, A. R. V. Dielectrics and Waves. N. York: J. Wiley, 1954.

Keywords: EMC, covers, shielding, coupled lines

**P. Drexler, P. Fiala**
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Methods for High Power EM Pulse Measurement

There are some suitable methods for the measurement of ultra-short solitary electromagnetic pulses that can be generated by high power pulsed generators. The measurement methods properties have to correspond to the fact whether we want to measure pulses of voltage, current or free-space electromagnetic wave. The need for specific measurement methods occurred by the development of high power microwave pulse generator. Applicable methods are presented in this paper. The method utilizing Faraday\'s induction law allows the measurement of generated current. For the same purpose the magneto-optic method can be utilized, with its advantages. For measurement of output microwave pulse of the generator the calorimetric method was designed and realized.

- FIALA, P. Non-conventional sources of electrical energy. Brno: BUT FEKT, 2003.
- FIALA, P., DREXLER, P., RYCHNOVSKY, J. Pulsed Power Generator with Output Power up to 20GW. Research report. HS Prototypa a.s., 18580001.
- BARKER, R. J., SCHAMILOGLU, E. High-Power Microwave Sources and Technologies. IEEE Press, 2001.
- DREXLER, P., KALAB, P., FIALA, P. Inductance-free high voltage divider for extreme conditions. In Proceeding of 16th International Conference on Dielectric and Insulating Systems in Electrical Engineering 2006. Casta-Pila (Slovakia), 2006, p. 168.
- RIORDAN, J. A., SUN, F.G., LU, Z.G., ZHANG, X.-C. Free-space transient magneto-optic sampling. Applied Physics Letters. 1997, vol. 71, p. 1452-1454.
- KASAL, M. Multinuclear Measuring Channel of NMR Spectrometer. Brno: FE BUT, 1984.
- PFEFFER, M., KASAL, M. Automatic Impulse Reflectometer. Sdelovaci technika,. 1986, vol. 10/11 (in Czech).
- SUNKA, P. Verbal information. UFP AV CR, Praha 6, 2003.
- PALISEK, L. The Alternative to Anti-Infantry Mines. Research report. VOP26, Sternberk. VTUPV Vyskov, 2005.
- CRAIG, A. E., CHANG, K. Optical Modulation: Magneto-Optical Devices. Handbook of Optical Components and Engineering. New Jersey: John Wiley & Sons, Inc., 2003. 1380 pages. ISBN 0-471-39055-0
- DREXLER, P. Methods for the Measurement of Ultrashort Electromagnetic Pulses. Treatise on the Ph.D. thesis. BUT FEKT, Brno, 2006.

Keywords: Electromagnetic pulse, high power microwave gene-rator, calorimetric method, magneto-optical effect, vircator

**V. Schejbal, D. Cermak, Z. Nemec, J. Pidanic, J. Konecny, P. Bezousek, O. Fiser**
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Multipath Propagation of UWB Through-Wall Radar and EMC Phenomena

The UWB (ultra wide band) radar output signals can be substantially affected due to electromagnetic wave propagation through obstacles (such as walls) and multipath effects, too. Multipath effects are analyzed and simulated numerically for various cases with several antenna heights and distances. Delays (due to propagation through walls and various paths of direct and reflected rays) and the ringing (similar to UWB propagation through wall) can be clearly observed and analyzed. Moreover, frequency spectra analyses can demonstrate both UWB interferences and susceptibility from electromagnetic compatibility (EMC) viewpoint.

- HEYMAN, E., MANDELBAUM, B., SHILOH, J. Ultra-Wideband Short-Pulse Electromagnetics 4. New York: Plenum Press, 1999.
- TAYLOR, J. D. Ultra-Wideband Radar Technology. N. York: CRC, 2001.
- BEZOUSEK, P., SCHEJBAL, V. Radar technology in the Czech Republic. IEEE Aerospace & Electronic Systems Magazine. 2004, vol. 19, no. 8, p. 27 - 34.
- SCHEJBAL, V. et al. UWB propagation through walls. Radioengieering. 2006, vol. 15, no. 1, p. 17 - 24.
- SCHEJBAL, V. et al. Electromagnetic wave propagation through obstacles. In International Workshop on Microwaves, Radar and Remote Sensing MRRS 2005. Kiev (Ukraine), 2005, p. 255 - 260.
- BEZOUSEK, P. et al. UWB signal propagation through walls. In International Workshop on Microwaves, Radar and Remote Sensing MRRS 2005. Kiev (Ukraine), 2005, p. 249 - 254.
- SCHEJBAL, V. et al. UWB radar signal propagation through walls and multipath effects. IEEE Aerospace & Electronic Systems Magazine. Submitted to publication.
- SCHEJBAL, V., CERMAK, D., NEMEC, Z., BEZOUSEK, P., FISER, O. Multipath propagation effects of UWB radars. In MIKON - 2006. Warszawa (Poland), 2006, p. 1188 - 1191.
- CERMAK, D., SCHEJBAL, V., NEMEC, Z., BEZOUSEK, P., FISER, O. UWB radar multipath propagation effects. In Scientific Papers of the University of Pardubice. Series B. The Jan Perner Transport Faculty 8 (2005).
- TAHA-AHMED, B., CALVO-RAMON, M., HARO-ARIET, L. Impact of UWB on macrocell downlink of DCS-1800 and GSM-900 systems. Radioengineering. 2005, vol. 14, no. 1, p. 51 -55.
- MOLISCH, A.F. Ultrawideband propagation channels-theory, measurement, and modeling. IEEE Transactions on Vehicular Technology. 2005, vol. 54, no. 5, p. 1528 - 1545.
- NEMEC, Z., MRKVICA, J., SCHEJBAL, V., CERMAK, D., BEZOUSEK, JERABEK, J., SIKL, R. UWB through-wall propagation measurements. Accepted for The 1st European Conf. on Antennas and Propagation. Nice, France, Nov. 6 - 10, 2006.

Keywords: UWB propagation, multipath effects, UWB radars, electromagnetic compatibility (EMC)

**J. Lettl, S. Fligl**
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Electromagnetic Compatibility of Matrix Converter System

The presented paper deals with matrix converters pulse width modulation strategies design with emphasis on the electromagnetic compatibility. Matrix converters provide an all-silicon solution to the problem of converting AC power from one frequency to another, offering almost all the features required of an ideal static frequency changer. They possess many advantages compared to the conventional voltage or current source inverters. A matrix converter does not require energy storage components as a bulky capacitor or an inductance in the DC-link, and enables the bi-directional power flow between the power supply and load. The most of the contemporary modulation strategies are able to provide practically sinusoidal waveforms of the input and output currents with negligible low order harmonics, and to control the input displacement factor. The perspective of matrix converters regarding EMC in comparison with other types of converters is brightly evident because it is no need to use any equipment for power factor correction and current and voltage harmonics reduction. Such converter with proper control is properly compatible both with the supply mains and with the supplied load. A special digital control system was developed for the realized experimental test bed which makes it possible to achieve greater throughput of the digital control system and its variability.

- GYUGYI, L., PELLY, B. R. Static Power Frequency Changers. New York: Wiley, 1976.
- ALESINA, A., VENTURINI, M. Analysis and design of optimum amplitude nine-switch AC-AC converters. IEEE Transactions on Power Electronics, 1989, vol. 4, no. 1, pp. 101-112.
- WEICHMANN, E. P., ESPINOZA, J. R., SALAZAR, L. D., RODRIGUEZ, J. R. A direct frequency converter controlled by space vectors. In Proceedings of PESC. 1993, pp. 314-320.
- HUBER, L., BOROJEVIC, D. Space vector modulation for forced commutated cycloconverters. In Proceedings of PESC. 1989, pp. 871-876.
- HORNKAMP, M., LODDENKOETTER, M., MUNZER, M., SIMON, O., BRUCKMAN, M. First IGBT module for matrix converter. Power Electronics Europe, 2001, issue 4.
- LETTL, J., FLIGL, S. Matrix converter in hybrid drives. In Proceedings of Problems of Present-day Electrotechnics Conference. Kyiv (Ukraine), 2004, vol. 3, pp. 77-80.
- LETTL, J., FLIGL, S. Matrix converter control system. In Proceedings of Progress in Electromagnetics Research Symposium. Hangzhou, 2005, pp. 395-398.

Keywords: Matrix converter, electromagnetic compatibility, pulse width modulation strategy, control system

**K. Jeong, M. Yokoyama, H. Uehara**
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A Robust Adaptive MMSE Rake Receiver for DS-CDMA System in a Fast Multipath Fading Channel

In this paper, we propose a robust adaptive minimum mean square error (MMSE) Rake receiver for asynchronous DS-CDMA systems. The receiver uses the modified MMSE criterion that incorporates the differential detection and the amplitude compensation for interference cancellation in a time-varying multipath fading channel. We investigate that the proposed Rake receiver can achieve the higher output signal to interference plus noise ratio (SINR) than the conventional adaptive Rake receiver, since the modified MMSE criterion does not attempt to track the time-varying MMSE solution. Computer simulations verify that the performance of the proposed Rake receiver is better than those of the conventional and the adaptive Rake receiver.

- MOSHAVI, S. Multi-user detection for DS-CDMA communications. IEEE Commun. Mag. 1996, vol. 34, no. 10, p. 124 - 136.
- KOULAKIOTIS, D., AGHVAMI, A. D. Data detection techniques for DS/CDMA mobile systems: a review. IEEE Pers. Commun. 2000, vol. 7, no. 3, p. 24-34.
- PROAKIS, J. G. Digital Communications. 3rd ed. McGraw-Hill, 1995.
- MILLER, S. L. An adaptive direct-sequence code-division multiple-access receiver for multiuser interference rejection. IEEE Trans.Commun. 1995, vol.43, no.2/3/4, pp.1746-1755.
- HONIG, M., MADHOW, U., VERDU, S. Blind adaptive multiuser detection. IEEE Trans. Inform. Theory. 1995, vol.41, no.4, pp. 944 to 960.
- LATVA-AHO, M., JUNTTI, M. J. LMMSE detection for DS-CDMA system in fading channels. IEEE Trans. Commun. 2000, vol. 48, no. 2, pp. 194-199.
- DEL RE, E., FANTACCI, R., MOROSI, S., PUGI, A. Advanced blind adaptive multi-user detector for communications in nonstationary multipath fading channel. IEEE Trans. Veh. Technol., 2001, vol. 50, no. 6, p. 1497-1056.
- LIU, T.-H. Linearly constrained minimum variance filters for blind multiuser detection. IEEE Trans. Commun. 2003, vol. 51, no. 10, p. 1649-1652.
- SKLAR, B. Rayleigh fading channels in mobile digital communication system. Part II: mitigation. IEEE Trans. Commun. Mag. July 1997, p. 102-109.
- TURIN, G. L. The effects of multipath and fading on the performance of direct-sequence CDMA systems. IEEE J. Select. Areas Commun. 1984, vol. SAC-2, no. 4, pp. 597-603.
- YOSHISA, S., USHIROKAWA, A., YANAGI, S., FURUYA, Y. DS/CDMA adaptive interference canceller on differential detection for fast fading channel. In Proc. 44-th Vehicular Technology Conference. 1994, p. 780-784.
- JEONG, K. S., YOKOYAMA, M., UEHARA, H. Performance improvement of MAI cancellation in fading DS/CDMA channels. IEICE Trans. Fundamentals. 2005, vol. E88-A, no. 10, p. 2869 to 2877.
- BARBOSA, A. N., MILLER, S. L. Adaptive detection of DS/CDMA signals in fading channels. IEEE Trans. Commun. 1998, vol.46, no.1, p.115-124.
- HAYKIN, S. Adaptive Filter Theory. Prentice Hall, 1996.

Keywords: DS-CDMA, modified MMSE, time-varying multipath fading, Rake receiver

**P. Smid, Z. Raida**
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Automated Modeling of Microwave Structures by Enhanced Neural Networks

The paper describes the methodology of the automated creation of neural models of microwave structures. During the creation process, artificial neural networks are trained using the combination of the particle swarm optimization and the quasi-Newton method to avoid critical training problems of the conventional neural nets.

In the paper, neural networks are used to approximate the behavior of a planar microwave filter (moment method, Zeland IE3D). In order to evaluate the efficiency of neural modeling, global optimizations are performed using numerical models and neural ones. Both approaches are compared from the viewpoint of CPU-time demands and the accuracy. Considering conclusions, methodological recommendations for including neural networks to the microwave design are formulated.

- RAIDA, Z. Modeling EM structures in the neural network Toolbox of MATLAB. IEEE Antennas & Propagation Magazine. 2002, vol. 44, no. 6, p. 46-67.
- RAYAS-SANCHEZ, J., E. EM-based optimization of microwave circuits using artificial neural networks: The state-of-the-art. IEEE Transactions on Microwave Theory and Techniques. 2004. no. 1, p. 402-434.
- RAHMAT-SAMII, Y., GIES, D., ROBINSON, J. Particle swarm optimization (PSO): A novel paradigm for antenna design. The Radio Science Bulletin. 2003, no. 305, p. 14-22.
- GUPTA, M. M., JIN, L., HOMMA, N. Static and Dynamic Neural Networks from Fundamentals to Advanced Theory. New Jersey: John Wiley & Sons, 2003.
- CHI D., D., SHIE-YUI, L. Generalization for Multilayer Neural Network Bayesian Regularization or Early Stopping.http://www.wrrc.dpri.kyoto-u.ac.jp/~aphw/APHW2004/proceedings/FWR/56-FWR-M185/56-FWR-M185%20(1).pdf

Keywords: Feed-forward neural network, recurrent neural network, particle swarm optimization

**J. Vochyan**
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Synthesis of New Biquad Filters Using Two CFOAs

This paper deals with synthesis based on new autonomous circuit using two current feedback operational amplifiers. Four possible second-order structures are derived and several active RC filters are described. One new circuit of the band-pass filter is introduced in detail. Its parameters are studied symbolically, tested by simulations and confirmed by measurements.

- FRANCO, S. Design with Operational Amplifiers and Analog Integrated Circuits. New York: The McGraw-Hill Companies, Inc., 1998. 668 pages. ISBN 0-07-021857-9.
- KOTON, J., VRBA, K. The design of frequency filters using autonomous circuits with the complete net of admittances. www.elektrorevue.cz, 2005. ISSN 1213-1539 (in Czech)
- BIOLEK, D., KOLKA, Z. SNAP: A tool for the analysis of analogue filters. In Proceedings of TSP99, Brno, 1999.
- PSpice Reference Guide, Cadence Design Systems, Inc., 2000.
- CHEN, W., BALLANCE, D. Stability analysis on the Nichols chart and its application in QFT. SIAM Journals Online, 1997. ISSN1095-7170.
- BIOLEK, D. The Possibilities of Electronic Adjusting of Second-Order Filters with Three Operational Amplifiers using Voltage Controlled Amplifiers. Research report GA CR no. 102/97/0765. University of Defense, Brno, Czech Republic, 1999. (in Czech)
- AD844 , Datasheets, Analog Devices, 2003.

Keywords: Active RC filters, current feedback operational amplifiers

**I. Hertl, Z. Raida, Z. Novacek**
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Multireflector Antennas - Cascaded Structures with Frequency Selective Surfaces

The problem of increasing the gain of directional multiband antennas is solved in the paper. A single-fed multiband (wideband) planar dipole is combined with cascaded (sandwiched) reflectors made of frequency selective surfaces. Each of those reflectors is placed in a quarter-wavelength distance from the dipole at the frequency of operation.

The impedance matching is particularly achieved by active element properties, and impedance symmetrization. Further transformation is made by a planar circuit, placed on the active element plane. The antenna gain is set by the reflector elements amount (reflector plane dimensions). The antenna structure enables its setting into arrays with in-phase feeding.

- CIAIS, P., STARAJ, R, KOSSIAVAS, G, LUXEY, C. Design of an internal quad-band antenna for mobile phones. IEEE Microwave and Wireless Components Letters. 2004, vol. 14, no. 4, p. 148-150.
- PALMERO, E., RAIDA, Z., RUIZ, R. Quad-band U-slot antenna for mobile applications. Radioengineering. 2006, vol. 15, no. 2, p. 22 29.
- HERTL, I. On multiband properties of printed dipole antenna. In Radioelektronika 2005 - conference proceedings. Brno (Czech Republic), 2005, p. 121 - 124.
- ENGARGIOLAX, G. Tapered Microstrip Balun for ATA Feed Development. ATA Memo 35 rev 1. (URL: http://astro.berkeley.edu/ral/ata/memos/memo35r1.pdf)
- WU T.-K., LEE S.-W. Multiband frequency selective surface with multiring patch elements. IEEE Transactions on Antennas and Propagation. 1994. vol. 42, no. 11, p. 1484 - 1490.

Keywords: Multiband antennas, directional antennas, frequency selective surfaces, cascaded structures

**R. Landqvist, A. Mohammed**
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Comparative Performance Analysis of Three Algorithms for Principal Component Analysis

Principal Component Analysis (PCA) is an important concept in statistical signal processing. In this paper, we evaluate an on-line algorithm for PCA, which we denote as the Exact Eigendecomposition (EE) algorithm. The algorithm is evaluated using Monte Carlo Simulations and compared with the PAST and RP algorithms. In addition, we investigate a normalization procedure of the eigenvectors for PAST and RP. The results show that EE has the best performance and that normalization improves the performance of PAST and RP algorithms, respectively.

- YANG, B. Projection approximation subspace tracking. IEEE Transactions on Signal Processing, 1995, vol. 32, p. 95-107.
- XU, L. Least mean square error reconstruction principle for self-organizing neural nets. Neural Networks, 1993, vol. 6, p. 627-648.
- PAJUNEN, P., KARHUNEN, J. Least-squares methods for blind source separation based on nonlinear PCA. International Journal of Neural Systems, 1997, vol. 8, p. 601-612.
- KARHUNEN, J., JOUTSENSALO, J. Representation and separation of signals using nonlinear PCA type learning. Neural Networks, 1994, vol. 7, p. 113-127.
- HAYKIN, S. Adaptive Filter Theory. Prentice Hall, 4th ed., 2002.
- RAO, Y. N., PRINCIPE, J. C. On-line principal component analysis based on a fixed-point approach. IEEE International Conference on Acoustics, Speech and Signal Processing, 2002, vol. 1, p. I-981-I-984.
- RAO, Y. N., PRINCIPE, J. C. A fast, on-line algorithm for PCA and its convergence characteristics. IEEE Signal Processing Society Workshop, 2000, vol. 1, p. 299-307.

Keywords: Principal component analysis, signal processing, exact eigen-decomposition

**Z. Lukes, J. Lacik, Z. Raida**
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Modeling and Optimizing Antennas for Rotational Spectroscopy Applications

In the paper, dielectric and metallic lenses are modeled and optimized in order to enhance the gain of a horn antenna in the frequency range from 60 GHz to 100 GHz. Properties of designed lenses are compared and discussed. The structures are modeled in CST Microwave Studio and optimized by Particle Swarm Optimization (PSO) in order to get required antenna parameters.

- TOWNES, C., H., SCHAWLOW, A., L. Microwave spectroscopy. Dover Publications, 1975.
- BALANIS, C. A. Antenna Theory: Analysis and Design. New York: John Wiley & Sons, 1997.
- MILLIGAN, T., A. Modern Antenna Design. New Jersey: John Wiley & Sons, 2005.
- http//www.cst.com
- ROBINSON, J., RAHAMAT-SAMII, Y. Particle swarm optimization in electromagnetics. IEEE Transactions on Antennas and Propagation, 2004, vol. 52, no. 2, p. 397-407.

Keywords: Horn antenna, dielectric lens, metallic lens, particle swarm optimization, rotational spectroscopy