December 2008, Volume 17, Number 4

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W. Tangsrirat [references] [full-text]
Electronically Tunable Multi-Terminal Floating Nullor and Its Applications

A realization scheme of an electronically tun- able multi-terminal floating nullor (ET-MTFN) is de- scribed in this paper. The proposed circuit mainly employs a transconductance amplifier, an improved translinear cell, two complementary current mirrors with variable current gain and improved Wilson current mirrors, which provide an electronic tuning of the current gain. The va- lidity of the performance of the scheme is verified through PSPICE simulation results. Example applications employing the proposed ET-MTFN as an active element demonstrate that the circuit properties can be varied by electronic means.

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  12. KANETSUKI, N., HIGASHIMURA, M., BEPPU, T., TSUKUTANI, T., FUKUI, Y. A realization of biquadratic circuit using MO-CCIIs and capacitors. In Proceedings of the 2003 International Technical Conference on Circuits, Systems, Computers and Communications, Kang-Won Do (Korea), 2003, vol. 3, p. 1615-1618.
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Keywords: Four-Terminal Floating Nullor (FTFN), Current Conveyor (CC), current-mode circuits.

T. Sutory, Z. Kolka [references] [full-text]
Characterization of Nonlinear Integrated Capacitors

The paper deals with a modified CBCM (Charge-Based Capacitance Measurements) method for nonlinear capacitance characterization. The method is characterized by high resolution although it is based on equipment found in any average laboratory. CBCM was originally developed for linear interconnect measurements. The proposed modification uses two DC swept sources to measure the whole nonlinear Q-v characteristic in both polarities without the necessity to switch the measured object. A test-chip implementing the method was designed and manufactured in the 0.35μm CMOS process. Verifica- tion against known capacitances proved the correctness and accuracy of the method. It was successfully used for MOSCAPs characterization.

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  8. VENDRAME, L., BORTESI, L., BOGLIOLO, A. Accuracy assessment and improvement of on-chip charge-based capacitance measurements. In Proceedings of the 7th IEEE SPI Workshop, Siena (Italy), 2003.
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Keywords: Charge-based capacitance measurements, structures, MOS capacitors, integrated circuits. test

D. Biolek, R. Senani, V. Biolkova, Z. Kolka [references] [full-text]
Active Elements for Analog Signal Processing: Classification, Review, and New Proposals

In the paper, an analysis of the state-of-the-art of active elements for analog signal processing is presented which support – in contrast to the conventional operational amplifiers – not only the voltage-mode but also the current- and mixed-mode operations. Several problems are addressed which are associated with the utilization of these elements in linear applications, particularly in frequency filters. A methodology is proposed which generates a number of fundamentally new active elements with their potential utilization in various areas of signal processing.

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Keywords: Active element, current conveyor, operational amplifier, OTA, CDBA, CDTA, filter.

W. Jaikla, M. Siripruchyanun, J. Bajer, D. Biolek [references] [full-text]
A Simple Current-Mode Quadrature Oscillator Using Single CDTA

This article presents a simple current-mode quadrature oscillator using a single Current Differencing Transconductance Amplifier (CDTA) as the active element. The oscillation condition and oscillation frequency can be electronically controlled. The circuit structure is very simple, consisting of merely one CDTA, one resistor and two capacitors. The proposed circuit is suitable for IC architecture. The PSpice simulation and experimental results are shown, and the results agree well with the theoretical assumptions.

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Keywords: Oscillator, CDTA, current-mode

P. Horsky [references] [full-text]
A Monotonic Precise Current DAC for Sensor Applications

In this paper a 17 bit monotonic precise current DAC for sensor applications is described. It is working in a harsh automotive environment in a wide temperature range with high output voltage swing and low current consumption. To guarantee monotonicity current division and segmentation techniques are used. To improve the output impedance, the accuracy and the voltage compliance of the DAC, two active cascoding loops and one follower loop are used. The resolution of the DAC is further increased by applying pulse width modulation to one fine LSB current. To achieve low power consumption unused coarse current sources are switched off. Several second order technological effects influencing final performance and circuits dealing with them are discussed.

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Keywords: Digital to analog converter, current output, segmentation, pulse width modulation, cascoding

L. Dolivka, J. Hospodka [references] [full-text]
Ways to Optimize Analogue Switched Circuits

This paper describes how analogue switched circuits (switched-capacitor and switched-current circuits) can be optimized by means of a personal computer. The optimization of this kind of circuits is not so common and their analysis is more difficult in comparison with continuously working circuits. Firstly, the nonidealities occurring in these circuits whose effect on their characteristics should be optimized are discussed. Then a few ways to analyze analogue switched circuits are shown. From all optimization algorithms applicable for this kind of optimization, two ones that seem to be the most promising are proposed. The differential evolution (one of evolutionary algorithms) combined with the simplex method was found to be most appropriate from these two ones. Two types of programs are required for the optimization of these circuits: a program for implementing calculations of the used optimization algorithm and a program for the analysis of the optimized circuit. Several suitable computer programs from both of the groups together with their proper settings according to authors’ experience are proposed. At the end of the paper, an example of a switched-current circuit optimization documenting the previous description is presented.

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Keywords: Optimization, switched-capacitor circuit, switched-current circuit, evolutionary algorithm.

O. Panagiev [references] [full-text]
Adaptive Compensation of the Nonlinear Distortions in Optical Transmitters Using Predistortion

The described method refers to compensation of nonlinear distortions, originating in laser diodes, used in wideband SCM-communication systems. Its essence is presenting in forming of a function that is opposite of the function describing the W-A characteristic of the emitting diode. Main element is the predistorter, which is connected in series before the emitting diode. This way, an improving of the optical transmitter’s parameters and characteristics is being realized, by using a purposive entering predistortion.

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Keywords: Nonlinear distortions, Predistorter, Laser diode, CSO, CTB, Volterra kernels.

J. Dobes [references] [full-text]
Using Volterra Series for an Estimation of Fundamental Intermodulation Products

The most precise procedure for determining the intermodulation products is to find a steady-state period of the signal first, and then to calculate its spectrum by means of the fast Fourier transform. However, this method needs time-consuming numerical integration over many periods of the faster signal even for enhanced methods for finding the steady state. In the paper, an efficient method for fast estimation of the fundamental intermodulation products is presented. The method uses Volterra series in a simple multistep algorithm which is compatible with a typical structure of the frequency-domain part of circuit simulators. The method is demonstrated by an illustrative testing circuit first, which clearly shows possible incorrect interpretation of the Volterra series. Thereafter, practical usage of the algorithm is demonstrated by fast estimation of the main intermodulation products of a low-voltage low-power RF CMOS fourquadrant multiplier.

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Keywords: Steady-state algorithm, fast Fourier transform, numerical integration, Volterra series, CMOS, RF multiplier

R. N. Baral, P. K. Singhal [references] [full-text]
Recent Techniques in Design and Implementation of Microwave Planar Filters

This paper details the techniques and initiatives made recently for improved response and simultaneous development of microwave planar filters. Although the objective of all the techniques is to design low cost filters with reduced dimensions, compact size with better frequency response, the methodological approaches are quite variant. The paper has gone through extensive analysis of all these techniques, their concept and design procedures.

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Keywords: Microstrip, Fractal, PBG (Photonic Band Gap), Defected Microstrip Structure (DMS), Defected Ground Structure (DGS).

P. Protiva, J. Mrkvica, J. Machac [references] [full-text]
Universal Generator of Ultra-Wideband Pulses

An Ultra-Wideband (UWB) subnanosecond pulse generator is described in this paper. High amplitude Gaussian pulses are generated by a Step Recovery Diode (SRD) included in a novel pulse forming circuit. The pro-posed circuit solution utilizes the performance of the SRD effectively, without excessive requirements regarding the driver section of the generator. Monocycle pulses are then generated by an additional pulse forming network. A sim-ple transistor driver is also described, which transforms a TTL trigger signal to a driving pulse with the timing and amplitude parameters required by the SRD. Measurement results are presented, which show the proposed generator operating with stable output pulse parameters at arbitrary pulse repetition frequency up to 20 MHz. The generated monocycle pulses are 25 V in amplitude and approximately 500 ps in width.

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Keywords: Ultra-Wideband, pulse generators, short pulses, step recovery diode, pulse shaping.

J. Haze, L. Fujcik, R. Vrba, M. Pavlik, L. Michaeli [references] [full-text]
The Utilization of Novel Bandpass Sigma-delta Modulator for Capacitance Pressure Sensor Signal Processing

The paper deals with a novel approach to processing of pressure sensor signals. A bandpass sigma-delta modulator is used for this purpose. This technique is relatively new and it is not used widely, because this kind of modulator is usually utilized for wireless and video applications. Since the bandpass sigma-delta modulator works within its defined band it is resistant to offsets of its sub-circuits. The main stages of this modulator are implemented by means of switched-capacitor (SC) technique. The article presents the basic ideas of this approach and simulation results of the first order of ideal and real modulator. The paper also shows the design of the phase locked loop (PLL) block for synchronization of sensor signal and modulator driving signal. The simple evaluation board was fabricated for confirmation of the proposed principle. Also shown are the results of the chip testing, the modulator layout and the design and test results of the second order of bandpass sigma-delta modulator briefly.

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Keywords: Bandpass sigma-delta modulation, pressure measurement, capacitance sensor.

M. Bobula, K. Danek, A. Prokes [references] [full-text]
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The rapid expansion of the digital signal processing has penetrated recently into a sphere of high performance industrial narrow band communication systems which had been for long years dominated by the traditional analog circuit design. Although it brings new potential to even increase the efficiency of the radio channel usage it also forces new challenges and compromises radio designers have to face. In this article we describe the design of the IF sampling industrial narrowband radio receiver, optimize a digital receiver structure implemented in a single FPGA circuit and study the performance of such radio receiver architecture. As an evaluation criterion the communication efficiency in form of maximum usable receiver sensitivity, co-channel rejection, adjacent channel selectivity and radio blocking measurement have been selected.

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Keywords: Radio receivers, radio telemetry, communication system performance, digital radio, software defined digital radio.

J. Lettl, R. Dolecek [references] [full-text]
EMC Increasing of PWM Rectifier in Comparison with Classical Rectifier

Pulse width modulated rectifier is a very popular topic nowadays. The modern industrial production demands continuous and lossless conversion of electrical energy parameters. This need leads to wide spread of power semiconductor converters. The rapid development in power electronics and microprocessor technology enables to apply sophisticated control methods that eliminate negative side effects of the power converters on the supply network. The phase controlled thyristor rectifiers overload the supply network with higher harmonics and reactive power consumption. That is why the PWM rectifier is being examined. In comparison with the phase controlled rectifier it can be controlled to consume nearly sinusoidal current with power factor equal to unity. Another advantage is its capability of energy recuperation. The PWM rectifier can assert itself for its good behavior in many applications, for example as an input rectifier in indirect frequency converter, or in traction. Traction vehicles equipped with PWM rectifier do not consume reactive power, do not load the supply network with higher harmonics, and the recuperation is possible. The paper deals with the PWM rectifier functional model realization and examination. Electromagnetic compatibility of PWM rectifier and classical phase controlled rectifier is compared on the basis of the input current harmonic analysis.

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Keywords: PWM rectifier, thyristor rectifier, pulse width modulation, control algorithm, measured waveforms, harmonic analysis, power factor.

J. Novak, J. Simanek, O. Cerny, R. Dolecek [references] [full-text]
EMC of Frequency Controlled Electric Drives

The paper deals with solution possibilities of EMC for voltage inverters, which uses PWM (Pulse Width Modulation). The paper offers solution of interference suppression which is raised by operation of frequency controlled drives. Possible interferences caused by inverters and their solutions are described at the first part of paper and real solution examples at the end of paper.

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Keywords: EMC, inverter, converter, sinus filter.

J. Holis, P. Pechac [references] [full-text]
Coexistence of Terrestrial and HAP 3G Networks during Disaster Scenarios

The aim of this paper is to show the possible coexistence of an HAP and a terrestrial component of 3G networks at a single carrier frequency. The main goal is to compare the basic parameters of terrestrial and HAP com-ponent 3G networks modeled in suburban (macrocell) and urban (macro/microcell) areas and to demonstrate the way they impact on each other. This study should present what we assume are the better capabilities of HAP 3G networks compared to their terrestrial counterparts. The parameters of the HAP and terrestrial component of 3G networks, were the terrestrial cells to be disabled during disasters, are also presented.

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  14. Minimum Performance Characteristics and Operational Conditions for High Altitude Platform Stations Providing IMT-2000 in the Bands 1885-1980 MHz, 2010-2025 MHz and 2110-2170 MHz and in Regions 1 and 3 and 1885-1980 MHz and 2110-2160 MHz in Region 2. Int. Telecommunications Union, Recommendation ITU-R M.1456, 2000.
  15. HOLIS, J., PECHAC, P. Provision of 3G mobile services in sparsely populated areas using High Altitude Platforms. Radioengineering, April 2008, vol. 17, no. 1, pp. 43-49.
  16. LAIHO, J., WACKER, A. NOVOSAD, T. Radio Network Planning and Optimization for UMTS. 2nd ed., John Wiley & Sons, 2005.
  17. SIAMITROS, K., DIMITRIOU, N., TAFAYOLLI, R. UMTS coverage planning using a High Altitude Platform Station (HAPS). In Proc. WPMC’02, Honolulu, 2002, pp. 1157-1159.
  18. HOLMA, H., TOSKALA, A. WCDMA for UMTS – HSPA Evolution and LTE. 4th ed., John Wiley & Sons, 2007.
  19. AXIOTIS, D. I., THEOLOGOU, M. E. 2 GΗz outdoor to indoor propagation at high elevation angles. In Proc. 13th International IEEE Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC), 2002, vol. 2, pp. 901–905.

Keywords: High altitude platforms (HAPs), UMTS, 3G, macro-, micro-cells.

S. Costanzo, G. D. Massa [references] [full-text]
Wideband Phase Retrieval Technique from Amplitude-Only Near-Field Data

A wideband frequency behavior is demonstrated for a phaseless near-field technique of basically interferometric approach, which uses two identical probes interfering each other through a microstrip circuit and performing amplitude-only near-field measurements on a single scanning surface. The phase retrieval procedure is properly formulated to take into account the frequency dependence without changing neither the microstrip circuit nor the distance between the probes. Numerical simulations on a linear array of elementary sources are presented to validate the theoretical results.

  1. JOHNSON, R. C., ECKER, H. A., HOLLIS, J. S. Determination of far-field antenna patterns from near-field measurements. Proc. of IEEE, 1973, vol. 61, no. 12, p. 1668 - 1694.
  2. YAGHAJIAN, A. D. An overview of near-field antenna measurements. IEEE Trans. Antennas Propag., 1986, vol. 34, no. 1, p. 30 - 45.
  3. COSTANZO, S., DI MASSA, G. Direct far-field computation from bi-polar near-field samples. Journal of Electr. Waves and Appl., 2006, vol. 20, no. 9, p. 1137 - 1148.
  4. COSTANZO, S., DI MASSA, G. Efficient near-field to far-field transformation from plane-polar samples. Microwave Opt. Tech. Letters., 2006, vol. 48, no. 12, p. 2433 - 2436.
  5. COSTANZO, S., DI MASSA, G. Near-field to far-field transformation with planar spiral scanning. Progress in Electromagnetics Research, PIER, 2007, vol. 73, p. 49 - 59.
  6. BUCCI, O. M., D’ELIA, G., LEONE, G., PIERRI, R. Far-field pattern determination from near-field amplitude on two surfaces. IEEE Trans. Antennas Propag., 1990, vol. 38, no. 11, p. 1772 to 1779.
  7. BUCCI, O. M., D’ELIA, G., LEONE, G., PIERRI, R. Far-field computation from amplitude-only near-field data on two surfaces: cylindrical case. IEE Proc. H., 1992, vol. 139, no. 2, p. 143 - 148.
  8. ISERNIA, T., LEONE, G., PIERRI, R. New approach to antenna testing from near-field phaseless data: the cylindrical scanning. IEE Proc. H., 1992, vol. 139, no. 4, p. 363 - 368.
  9. FARHAD RAZAVI, S., RAHMAT-SAMII, Y. A new look at phaseless planar near-field measurements: limitations, simulations, measurements, and a hybrid solution. IEEE Antennas and Propagation Magazine, 2007, vol. 49, no. 2, p. 170 - 178.
  10. COSTANZO, S., DI MASSA, G., MIGLIORE, M. D. A novel hybrid approach for far-field characterization from near-field amplitudeonly measurements on arbitrary scanning surfaces. IEEE Trans. Antennas Propag., 2005, vol. 53, no. 6, p. 1866 - 1874.
  11. BUCCI, O. M., GENNARELLI, C., SAVARESE, C. Representation of electromagnetic fields over arbitrary surfaces by a finite and nonredundant number of samples. IEEE Trans. Antennas Propag., 1998, vol. 46, p. 351 - 359.

Keywords: Near-field methods, phase-retrieval, antenna measurements.

D. Bonefacic, B. Rapinac, J. Bartolic [references] [full-text]
Slotted PIFA for Mobile Communication Devices

Slotted PIFA with capacitive loading for operation in the 880 / 960 MHz band is presented. The PIFA is intended for mobile terminals in GSM mobile communication network. The antenna is placed on a ground plane with dimensions of an average handheld device. It is optimized by using electromagnetic simulator and a prototype is manufactured. Calculated and measured results agree very well. Input impedance matching with SWR < 3 in the whole band was achieved. Maximum gain of 3.2 dBi is measured. Preliminary studies of the influence of the user\'s head and hand on the antenna characteristics have been performed.

  1. WHEELER, H. A. Fundamental limitations of small antennas. Proceedings of the IRE, 1947, vol. 35, pp. 1479-1484.
  2. CHU, L. J. Physical limitation on omni-directional antennas. Journal of Applied Physics, 1948, vol. 19, pp. 1163-1175.
  3. SKRIVERVIK, A. K., ZURCHER, J.-F., STAUB, O., MOSIG, J. R. PCS antenna design: The challenge of miniaturization. IEEE Antennas and Propag. Magazine, 2001, vol. 43, no. 4, pp. 12 to 26.
  4. MARTINEZ-VAZQUEZ, M. ACE small terminal antennas activities: a review of the state of the art. In Proc. of the 18th Int. Conference on Applied Electromagnetics and Communications (ICECom 2005). Dubrovnik (Croatia), 2005, pp. 29 to 32.
  5. WONG, K.L. Planar Antennas for Wireless Communications. Hoboken (New Jersey, USA): J. Wiley, 2003.
  6. HIRASAWA, K. Small antennas for mobile communications. In Proceedings Antenn00, Nordic Antenna Symposium. Lund (Sweden), 2000, pp. 11 - 15.
  7. KAN, H. K., WATERHOUSE, R. B. Small printed-wing antenna suitable for wireless handset terminals. Microwave and Optical Technology Letters, August 2001, vol. 30, no. 4, pp. 226 - 229,
  8. CHAIR, R., LUK, K. M., LEE, K. F., Miniature multilayer shorted patch antenna. Electronics Letters, 2000, vol. 36, no. 1, pp. 3 - 4.
  9. CHAIR, R., LUK, K. M., LEE, K. F. Miniature shorted dual-patch antenna. IEE Proc.-Microw. Antennas Propag., 2000, vol. 147, no. 4, pp. 273 - 276.
  10. KUO, J. S., WONG, K.-L. A low-cost microstrip-line-fed shorted-patch antenna for a PCS base station. Microwave and Optical Technology Letters, 2001, vol. 29, no. 3, pp. 146 - 148.
  11. VIRGA, K. L., RAHMAT-SAMII, Y. Low-profile enhanced-bandwidth PIFA antennas for wireless communications packaging. IEEE Transactions on Microwave Theory and Techniques, 1997, vol. 45, no. 10, pp. 1879 - 1888.
  12. HERSCOVICI, N., FUENTES OSORIO, M., PEIXEIRO, C. Minimization of a rectangular patch using genetic algorithms. In Proceedings of the 18th International Conference on Applied Electromagnetics and Communications (ICECom 2005). Dubrovnik (Croatia), 2005, pp. 37 - 40.
  13. KUMAR, G., RAY, K. P. Broadband Microstrip Antennas. Norwood (MA, USA): Artech House, 2003.
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  15. http://www.ansoft.com/products/hf/hfss/

Keywords: Small antenna, microstrip antenna, planar-inverted-F antenna, PIFA.

P. Kovacs, Z. Raida, M. Martinez-Vazquez [references] [full-text]
Parametric Study of Mushroom-like and Planar Periodic Structures in Terms of Simultaneous AMC and EBG Properties

In the paper, the parametric analysis of a mushroom-like and a planar metallo-dielectric periodic structure with square unit cell and metallic patch is presented. First, the angular stability for different unit cell settings was studied. Second, restrictions for simultaneous behavior as artificial magnetic conductor (AMC) and electromagnetic band gap (EBG) are briefly discussed. Finally, main differences between the mushroom-like and the planar structure are specified and conclusions are formulated.

  1. SIEVENPIPER, D., ZHANG, L., BROAS, R. F. J, ALEXOPOLUS, N. G., YABLONOVITCH, E. High-impedance electromagnetic surfaces with a forbidden frequency band. IEEE Trans. on Microwave Theory and Techniques, 1999, vol. 47, no.11, p. 2059 – 2074.
  2. GOUSETTIS, G., FRESEDIS, A. P., VARDAXOGLOU, Y. C. Tailoring the AMC and EBG characteristics of periodic metallic arrays printed on grounded dielectric substrate. IEEE Transactions on Antennas and Propagation, January 2006, vol. 54, no.1, pp. 82-89.
  3. MONORCHIO, A., GENOVESI, S., SERRA, U., MANARA, G. Optimal design of artificial magnetic conductors including angular response. IEEE Antennas and Propagation Society International Symposium, 9-14 July, 2006, pp. 1931-1934.

Keywords: Artificial magnetic conductor, electromagnetic band gap, mushroom and planar structure, angular stability

B. M. Vidal, Z. Raida [references] [full-text]
Synthesizing Sierpinski Antenna by Genetic Algorithm and Swarm Optimization

The paper discusses the synthesis of the Sierpinski antenna operating at three prescribed frequencies: 0.9 GHz, 1.8 GHz (both GSM) and 2.4 GHz (Bluetooth). In order to synthesize the antenna, a genetic algorithm and a particle swarm optimization were used. The numerical model of the antenna was developed in Zeland IE3D, optimization scripts were programmed in MATLAB. Results of both the optimization methods are compared and experimentally verified.

  1. MANDELBROT, B.B. The Fractal Geometry of Nature. New York: W.H. Freeman and Company, 1982.
  2. HAZDRA, P. Compact Fractal Antenna Structures. Technical Thesis. Prague: Czech Technical University, 2005.
  3. PUENTE, C., ROMEU, J., POUS, R., CARDAMA, A. On the behavior of the Sierpinski multiband antenna. IEEE Transactions on Antennas and Propagation, 1998, vol. 46, no. 4, p. 517–524.
  4. MONTOYA, A. Fractal Antennas (Antenas Fractales: un paso en la evolucion de las Telecomunicaciones). Mendellin-Colombia: Universidad de Antioquia. (In Spanish)
  5. SIAH, E. S., OOI, B. L., KOOI, P. S., XHOU, X. D. Experimental investigation of several novel fractal antennas-variants of the Sierpinski Gasket and introducing fractal FSS screens. In Proceedings of the 1999 Asia Pacific Microwave Conference, vol. 1, p. 170 – 173, 1999.
  6. ROBINSON, J., RAHMAT-SAMII, Y. Particle swarm optimization in electromagnetics. IEEE Transactions on Antennas and Propagation, 2004, vol. 52, no. 2, p. 397–407.
  7. GARCIA, J. M., ALBA E., LUQUE G. J. Algoritmos Basados en Cumulos de Particulas Para la Resolucion de Problemas Complejos. 2006. (In Spanish.)
  8. PEREZ LOPEZ, J. R. Contribucion a los metodos de optimizacion basados en procesos naturales y su aplicacion a las medidas de campo proximo. Santander: Universidad de Santander, 2005. (In Spanish.)
  9. TOWNSEND, A.A.R. Genetic Algorithm – A Tutorial [online]. Av.: www-course.cs.york.ac.uk/evo/SupportingDocs/TutorialGAs.pdf
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  12. IE3D User’s Manual. Fremont: Zeland Software, Inc., 2006.

Keywords: Fractal antenna, Sierpinski monopole, particle swarm optimization, genetic algorithm.

P. V. Y. Jayasree, V. S. S. N. S. Baba, B. P. Rao [references] [full-text]
Shielding Effectiveness of Laminated Shields

Shielding prevents coupling of undesired radiated electromagnetic energy into equipment otherwise susceptible to it. In view of this, some studies on shielding effectiveness of laminated shields with conductors and conductive polymers using plane-wave theory are carried out in this paper. The plane wave shielding effectiveness of new combination of these materials is evaluated as a function of frequency and thickness of material. Conductivity of the polymers, measured in previous investigations by the cavity perturbation technique, is used to compute the overall reflection and transmission coefficients of single and multiple layers of the polymers. With recent advances in synthesizing stable highly conductive polymers these lightweight mechanically strong materials appear to be viable alternatives to metals for EM1 shielding.

  1. NAARMAN, H. Synthesis of new conductive electronic polymers. In Proc. Int. Cong. Synthetic Metals. Kyoto (Japan), June 1986.
  2. EHINGER, K., SUMMERFIELD, S., BAUHOFER, W., ROTH, S. DC and microwave conductivity of iodine-doped polyacetylene. J . Phys. C: Solid State Phys., 1984, vol. 17, pp. 3753-3762.
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  5. KONEFAL, T., DAWSON, J. F., MARVIN, A. C. Improved aperture model for shielding prediction. In IEEE International Symposium on Electromagnetic Compatibility, pp. 187-192, 2003.
  6. PRASAD KODALI, V. Engineering Electromagnetic Compatibility, Principles, Measurements and Technologies. S. Chand & company Ltd., 2000.
  7. PAUL, R. C. Introduction to Electromagnetic Compatibility. New York: John Wiley Interscience, 1992.
  8. SCHULZ, R. B., PLANTZ, V. C., BRUSH, D. R. Shielding theory and practice. IEEE Trans. Electromagn. Compat., Aug. 1988, vol. 30, pp. 187-201.

Keywords: Laminated shield, shielding effectiveness, frequency, conductive polymer.

R. N. Baral, P. K. Singhal [references] [full-text]
Design of Microstrip Band Pass Fractal Filter for Suppression of Spurious Band

In this paper, the design and subsequent fabrication of a hairpin-line band pass filter has been proposed. This filter exhibits periodic frequency response. By proper design, the spurious bands are being suppressed significantly through the implementation of Koch fractal on the microstrip coupled line.

  1. Hong Jia-Shen, G., Lancaster, M. J. Microstrip Filters for RF/ Microwave Applications. John Wiley & Sons Inc., 2001.
  2. Pozar, D. M. Microwave Engg. John Wiley, 2000.
  3. Hsieh, Y., Wang, S.-M., Chang, C.-Y. Bandpass filters with resistive attenuators being located at 2nd and 4th spurious. In Proc. 34 rd EuMC, 2004, vol. 2, p. 729 – 732.
  4. Mandelbrot, B. B. The Fractal Geometry of Nature. New York: W. H. Freeman, 1983.
  5. Jaggard, D. L. On Fractal Electrodynamics. Recent Advances in Electromagnetic Theory. Ed. H N Kriticos and D L Jaggard. New York: Springer-Verlag, 1990.
  6. Kwon Kim, Il., et. al. Fractal-shaped microstrip coupled-line bandpass filters for suppression of second harmonic. IEEE Transactions on Microwave Theory and Techniques, 2005, vol. 53, no. 9, p. 2943 – 2948.
  7. IE3D Software Release – 8, Developed by M/s Zeland Software Inc.
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Keywords: Hairpin-line, Koch fractal, band pass filter, spurious band.

H. Chaker, S. M. Meriah, F. T. Bendimerad [references] [full-text]
Optimization of Micro Strip Array Antennas Using Hybrid Particle Swarm Optimizer with Breeding and Subpopulation for Maximum Side-Lobe Reduction

In this paper, a technique based on hybrid particle swarm optimiser with breeding and subpopulation is presented for optimal design of reconfigurable dual-beam linear array antennas and planar arrays. In the amplitudephase synthesis, the design of a reconfigurable dual-pattern antenna array is based on finding a common amplitude distribution that can generate either a pencil or sector beam power pattern, when the phase distribution of the array is modified appropriately. The goal of this study is to introduce the hybrid model to the electromagnetic community and demonstrate its great potential in electromagnetic optimizations.

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  2. GIES, D., RAHMAT-SAMII, Y. Particle swarm optimization for reconfigurable phase differentiated array design. Microwave and Optical Technol. Lett., August 2003, vol. 38, no. 3, pp. 168-175.
  3. ROBINSON, J., RAHMAT-SAMII, Y. Particle swarm optimization in Electromagnetic. IEEE Trans. Antennas & Propagation, Feb.2004, vol. 52, no. 2, pp. 397-407.
  4. ROBINSON, J., SINTON, S., RAHMAT-SAMII, Y. Particle swarm, genetic algorithm, and their hybrids: Optimization of a profiled corrugated horn antenna. IEEE AP-S, 2002, pp. 314-317.
  5. LOVBJERG, M., RASMUSSEN, T. K., KRINK, T. Hybrid particle swarm optimizer with breeding and subpopulations. In Proceedings of the Genetic and Evolutionary Computation Conference (GECCO). San Francisco (USA), July 2001.
  6. MERIAH, S. M., BENDIMERAD, F.T. Low level side lobes in thinned antennas arrays by switched supply law. Optimization by genetic algorithm. Annals of Telecommunications. 55, N°11-12, 2000, pp. 615-621.
  7. SPEARS, W. M. Simple subpopulation schemes. In Proceeding of the Evolutionary Programming Conference, 1994, pp. 296-307.
  8. KENNEDY, J., EBERHART, R. C. Particle swarm optimization. In Proceeding of the 1995 IEEE International Conference on Neural Networks, vol. 4, p. 1942-1948.
  9. SHI, Y., EBERHART, R. C. A modified particle swarm optimizer. IEEE International Conference on Evolutionary Computation. Anchorage (Alaska), May 4-9, 1998.
  10. SHI, Y., EBERHART, R. C. Parameter selection in particle swarm optimization. Evolutionary programming VII (1998), lecture notes in computer science 1447, 591-600. Springer
  11. KENNEDY, J. Small words and mega-minds: Effects of neighbourhood topology on particle swarm performance. In Proceedings of the 1999 Congress of Evolutionary Computation, vol. 3, p. 1931-1938. IEEE Press.
  12. MAHANTI, G. K., DAS, S., CHAKRABORTY, A. Design of phasedifferentiated reconfigurable array antennas with minimum dynamic range ratio. In IEEE Antennas and Wireless Propagation Letters, 2006, vol. 5, p. 262-264.

Keywords: Hybrid particle swarm, breeding and subpopulation, global optimization, phased array, reconfigurable array, planar array.

K. B. Baltzis [references] [full-text]
An Efficient Finger Allocation Method for the Maximum Likelihood RAKE Receiver

In wideband wireless communication systems the RAKE receiver is commonly used to collect the resolvable multipath energy and counter the effects of fading through diversity. However, in channels with large delay and energy spread, its high complexity still remains a major issue. This motivates the study and application of computationally efficient finger placement algorithms that significantly reduce the receiver complexity with a reasonable performance loss. In this paper, a low–complexity maximum likelihood RAKE receiver, the Suboptimum – Maximum Power Minimum Correlation (S–MPMC) RAKE is proposed. The allocation of its first two fingers is based on the received signal correlation properties. Their positions determine also the placement of the rest of the fingers. Simulation results are provided to show the operation of the receiver and demonstrate its performance. Comparisons with relevant methods are performed to corroborate the merits of the proposal. The balance on the performance and the complexity of the technique makes it suitable for use in commercial wideband communication systems.

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  13. SUI, H., MASRY, E., RAO, B. D. Chip-level DS-CDMA downlink interference suppression with optimized finger placement. IEEE Transactions on Signal Processing, 2006, vol. 54, no. 10, p. 3908 to 3921.
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  16. CASSIOLI, D., WIN, M. Z., VATALARO, F., MOLISCH, A. F. Low complexity rake receivers in ultra-wideband channels. IEEE Transactions on Wireless Communications, 2007, vol. 6, no. 4, p. 1265-1275.
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  19. KIM, Y. W., KIM, Y. V., KIM, J. H., CHO, H.-S., SUNG, D. K. A comparison of system performance using two different chip pulses in multiple-chip-rate DS/CDMA systems. IEEE Transactions on Communications, 2001, vol. 49, no. 11, p. 1988-1996.
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  22. COELLO, C. A. C., LAMONT, G. B., VAN VELDHUIZEN, D. A. 2nd ed. Evolutionary Algorithms for Solving Multi-Objective Problems. Berlin: Springer, 2007.
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  25. BOTTOMLEY, G. E., CAIRNS, D. A., COZZO, C., FULGHUM, T. L., KHAYRALLAH, A. S., LINDELL, P., SUNDELIN, M., WANG, Y.-P. Advanced receivers for WCDMA terminal platforms and base stations. Ericsson Review, 2006, vol. 8, no. 2, p. 54-58.

Keywords: Code division multiple access, correlation, maximum likelihood detection, multipath channels, rake diversity, wireless communication

Z. Nemec, P. Bezousek [references] [full-text]
The Time Difference of Arrival Estimation of Wi-Fi Signals

The papers deals with a modeling of a Time- Difference of Arrival system for a subscriber station localization, based on the 802.11 standard wireless network. In the case of severe multipath effects the standard TDOA estimation methods, based on correlation of signals, received by conveniently displaced receiving stations show large errors. Thus, a new algorithm is proposed using received signals decomposition to a set of delayed replicas. This represents a linear estimation of reflected signals amplitudes. The described method leads to a better estimation of time differences of the signals, propagating on the direct paths between the emitter and the receiving stations.

  1. WOLFLE, G., HOPPE, R., ZIMMEMANN, D., LANDSTORFER, F. Enhanced localization technique within urban and indoor enviroments based on accurate and fast propagation models. European Wireless 2002, Firence (Italy), 2002.
  2. VELAYOS, H., KARLSSON, G. Limitations of range estimation in wireless LAN. In Proceedings of the 1st Workshop on Positioning, Navigation and Communication. Germany, 2004.
  3. BEZOUSEK, P. Position and velocity measurement accuracy analysis of the FMCW multilateration sensor. Scientific Papers of the University of Pardubice, Series B – The Jan Perner Transport Faculty 10, p. 5-17, Pardubice, 2004.
  4. NEMEC, Z. Application of a Data Communication to a Mobile Station Localization (in Czech). Dissertation, The Jan Perner Transport Faculty, University of Pardubice, 2007.

Keywords: Positioning, multipath propagation, correlated signals, wall reflections, signal parameters estimation, signal processing.

M. Vondrasek, P. Sovka, T. Tichy [references] [full-text]
ACE Strategy with Virtual Channels

Cochlear implant is an electronic device, which can mediate hearing sensations to profoundly deaf people. Contemporary cochlear implants are sophisticated electronic devices; however, their performance could still be improved.
This paper describes an experiment we made in that direction: additional 21 virtual channels were implemented by sequential stimulation of adjacent intracochlear electrodes, and the ACE strategy with virtual channels (ACEv, Advanced Combination Encoder strategy with virtual channels) for the Nucleus® 24 Cochlear Implant System was created and verified in a clinical test with four patients.

  1. CLARK, G. Cochlear Implants, Fundamentals and Applications. New York: Springer NY, 2003. 830 p. ISBN 0-387-95583-6.
  2. ACE and CIS DSP Strategies. Software Requirements Specification, Cochlear Ltd. Australia, 2002.
  3. LAN, H., NIE, K. A Novel speech-processing strategy incorporating tonal information for cochlear implants. IEEE Transactions on Biomedical Engineering, 2004, vol. 51, no. 5, p. 752-760. ISSN 0018-9294.
  4. TONGOLA, G., BASSELI, M. Wavelet speech processing for cochlear implants. In EMBEC 2005, Prague (Czech Republic), 20-25 Nov. 2005.
  5. WILSON, B., ZERBI, M., LAWSON, D. Identification of virtual channel conditions on the basis of pitch. Third Quarterly Progress Report, NIH project NOI-DC-2-2401.
  6. POROY, O., LOIZOU, P. C. Pitch perception using virtual channels. In Conference on Implantable Auditory Prostheses, Asilomar, Monterey, CA, 2001.
  7. BUSBY, P. A., PLANT, K. Dual electrode stimulation using the Nucleus CI24RE cochlear implant: Electrode impedance and pitch ranking studies. Ear & Hearing, October 2005, vol. 26, no. 5, p. 504- 511.
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Keywords: Cochlear Implant, Virtual Channels, Speech Processing.

I. Baronak, P. Kvackaj [references] [full-text]
A New CAC Method Using Queuing Theory

The CAC (Connection Admission Control) method plays an important role in the ATM (Asynchronous Transfer Mode) network environment. The CAC is the first step in the prevention of congested states in the network topology, and conducts to the optimal network resources utilization.
The paper is aimed to propose an enhancement for a convolution method that is one of the statistical CAC methods used in ATM. The convolution method uses a buffer-less assumption in the estimation of the cell loss. Using formulas for the G/M/1 queuing system, the cell loss can be estimated as the buffer overflow probability.
In this paper, the proposed CAC method is compared with other three statistical CAC methods, and conclusions regarding the exploitation of the CAC method are presented.

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Keywords: Connection Admission Control (CAC), Asynchronous Transfer Mode (ATM), convolution method.

M. Dobrovolny, P. Bezousek, M. Hajek [references] [full-text]
Application of a Cumulative Method for Car Borders Specification in Image

The paper deals with low-level car detection methods in images. The car detection is an integral part of all intelligent car cruise systems. This article describes the method for suppression of the edges produced by classical edge\'s operators, based on application of the cumulative method. The designed method uses the non-stationary property of the picture background in time-realizations of the image signal.

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Keywords: Image processing, cumulative method, Intelligent Driver Systems (IDS), car detection, edge detection.

M. Adam, F. Rossant, F. Amiel, B. Mikovikova, T. Ea [references] [full-text]
Eyelid Localization for Iris Identification

This article presents a new eyelid localization algorithm based on a parabolic curve fitting. To deal with eyelashes, low contrast or false detection due to iris texture, we propose a two steps algorithm. First, possible edge candidates are selected by applying edge detection on a restricted area inside the iris. Then, a gradient maximization is applied along every parabola, on a larger area, to refine parameters and select the best one. Experiments have been conducted on a database of 151 iris that have been manually segmented. The performance evaluation is carried out by comparing the segmented images obtained by the proposed method with the manual segmentation. The results are satisfactory in more than 90% of the cases.

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Keywords: Biometric identification, iris analysis, eyelid segmentation, edge selection, curve fitting.

F. Rossant, F. Amiel, T. Ea, C. M. Martinez, M. Paques [references] [full-text]
Enhancement of Optical Coherence Tomography Images of the Retina by Normalization and Fusion

This paper describes an image processing method applied to Optical Coherence Tomography (OCT) images of the retina. The aim is to achieve improved OCT images from the fusion of sequential OCT scans obtained at identical retinal locations. The method is based on the normalization of the acquired images and their fusion. As a result, a noise reduction and an image enhancement are reached. Thanks to the resulting improvement in retinal imaging, clinical specialists are able to evaluate more efficiently eyes pathologies and anomalies. This paper presents the proposed method and gives some evaluation results.

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Keywords: Optical coherence tomography, denoising, filtering, correlation, fusion

B. Godara, A. Fabre [references] [full-text]
A New Application of Current Conveyors: The Design of Wideband Controllable Low-Noise Amplifiers

The aim of this paper is three-fold. First, it reviews the low-noise amplifier and its relevance in wireless communications receivers. Then it presents an exhaustive review of the existing topologies. Finally, it introduces a new class of LNAs, based on current conveyors, describing the founding principle and the performances of a new single-ended LNA. The new LNAs offer the following notable advantages: total absence of passive elements (and the smallest LNAs in their respective classes); wideband performance, with stable frequency responses from 0 to 3 GHz; easy gain control over wide ranges (0 to 20 dB). Comparisons with other topologies prove that the new class of LNA greatly advances the state of the art.

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Keywords: All-transistor circuits, low-noise amplifiers, multiband receivers, wideband RF circuits.

P. Drexler, P. Fiala [references] [full-text]
Utilization of Faraday Mirror in Fiber Optic Current Sensors

Fiber optic sensors dispose of some advantages in the field of electrical current and magnetic field measurement, like large bandwidth, linearity, light transmission possibilities. Unfortunately, they suffer from some parasitic phenomena. The crucial issue is the presence of induced and latent linear birefringence, which is imposed by the fiber manufacture imperfections as well as mechanical stress by fiber bending. In order to the linear birefringence compensation a promising method was chosen for pulsed current sensor design. The method employs orthogonal polarization conjugation by the back direction propagation of the light wave in the fiber. The Jones calculus analysis presents its propriety. An experimental fiber optic current sensor has been designed and realized. The advantage of the proposed method was proved considering to the sensitivity improvement.

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Keywords: Fiber optic sensor, magneto-optic effect, Faraday mirror, linear birefringence, circular birefringence.

H. Blasinsky, F. Amiel, T. Ea, F. Rossant, B. Mikovicova [references] [full-text]
Implementation and Evaluation of Power Consumption of an Iris Pre-processing Algorithm on Modern FPGA

In this article, the efficiency and applicability of several power reduction techniques applied on a modern 65nm FPGA is described. For image erosion and dilation algorithms, two major solutions were tested and compared with respect to power and energy consumption. Firstly the algorithm was run on a general purpose processor (gpp) NIOS and then hardware architecture of an Intellectual Property (IP) was designed. Furthermore IPs design was improved by applying a number of power optimization techniques. They involved RTL level clock gating, power driven synthesis with fitting and appropriate coding style. Results show that hardware implementation is much more energy efficient than a general purpose processor and power optimization schemes can reduce the overall power consumption on an FPGA.

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Keywords: FPGA, power optimization, dilation, erosion, general purpose processor, SoPC.

K. Bartusek, P. Fiala, J. Mikulka [references] [full-text]
Numerical Modeling of Magnetic Field Deformation as Related to Susceptibility Measured with an MR System

The possibility is studied of numerical modeling of magnetic field deformations in the environment of measured diamagnetic and paramagnetic samples for the purposes of studying magnetic resonance (MR) image deformations owing to the susceptibility of heterogeneous materials (objects). The verification was realized using a simple sample configuration (circular plate), and the numerically modeled cross-sections were compared with the experimentally obtained values of the magnetic field measured by the MR gradient echo technology. The results show that it is possible – via a technical calculation – to determine a magnetic field deformation in the environment of complex-shaped or non-homogeneous structures in the MR experiments.

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Keywords: Magnetic resonance (MR), numerical modeling, magnetic resonance imaging (MRI), magnetic field mapping, finite element method (FEM).

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