# September 2007, Volume 16, Number 3

**P. Kucera**
[references] [full-text]

Quantum Description of Optical Devices Used in Interferometry

A quantum-mechanical description of the phase shifters, retarders, mirrors and beam splitters is given in the paper. The description is then applied on two types of states. On a coherent state, a classical-like state, and on a number state, hence the strict quantum state.

The quantum description of a beam splitter can be found in the literature. However the description does not treat with the polarization concept.

The paper is aimed to introduce quantum description of an arbitrary oriented retarder and give a description of a beam splitter which treats with the polarization.

- GERRY, C. C., KNIGHT P. L. Introductory Quantum Optics. Cambridge University Press, 2005, ISBN 0 521 52735 X.
- NIELSEN, M. A., CHUANG, I. L. Quantum Computation and Quantum Information. Cambridge University Press, 2000, ISBN 0-521-63503-9.
- LOUDON, R. The Quantum Theory of Light. Oxford University Press, 2000, ISBN 0-19-850176-5.

Keywords: Phase shifter, retarder, beam splitter, polarization, coherent state, number state, Jones calculus

**R. Kvicala, V. Kvicera, M. Grabner, O. Fiser**
[references] [full-text]

BER and Availability Measured on FSO Link

The BER and the availability belong among the basic qualitative parameters of free space optical (FSO) links. The BER parameter is usually mentioned by FSO manufacturers, but it is not defined what conditions a certain value of BER stands for. This article deals with problems of measuring the BER of free space optical link and with questions how to determine the probability of unavailability of a certain link. The implementation of bit error rate tester with the E1 interface system is presented. In the article the statistics of the meteorological optical range for the year 2006 are shown. Using these data one can determine the probability of a certain value of atmospheric attenuation that influences the link unavailability.

- KIM, I. I., KOREVAAR, E. Availability of free space optics (FSO) and hybrid FSO/RF systems. In Proc. of Optical Wireless Communications IV. SPIE 4530, 2001, p. 84-95.
- KIM, I., I., MCARTHUR, B., KOREVAAR, E. Comparison of laser beam propagation at 785 nm and 1550 nm in fog and haze for optical wireless communications. In Proc. of SPIE, vol. 4214 Optical Wireless Communications III, ed. Eric J. Korevaar, 2001, p. 26-37.
- ANDREWS, L. C., PHILLIPS, R. L., HOPEN, C. Y. Laser Beam Scintillation with Applications. Washington: SPIE Press, 2001.
- ITU-T G.827: Availability Performance Parameters and Objectives for End-to-End International Constant Bit-Rate Digital Paths. ITU, Geneva, 2003.
- ITU-T O.151: Error Performance Measuring Equipment Operating at the Primary Rate and Above. ITU, Geneva, 1992.

Keywords: Free space optical link, quality of service, meteorological optical range, link unavailability, bit error rate

**A. Prokes**
[references] [full-text]

Influence of Temperature Variation on Optical Receiver Sensitivity and its Compensation

In the paper, the influence of temperature variation on the sensitivity of an avalanche-photodiode-based optical receiver applied in the free space optical communication link is discussed. Communication systems of this type are exposed to a wide range of operating temperatures, which markedly affect many photodiode and preamplifier parameters. The paper presents a receiver sensitivity calculation, taking into consideration the temperature dependence of avalanche photodiode gain, excess noise factor, dark current and thermal noise of preamplifier resistances, and describes the compensation of temperature effects on photodiode gain based on a corresponding change in the reverse voltage applied to the diode. The calculations are demonstrated on the connection of a small-area silicon APD operating in the wavelength range from 820 to 1150 nm with a transimpedance preamplifier using a bipolar junction transistor.

- ALEXANDER, B. S. Optical Communication Receiver Design. SPIE Optical Engineering Press, Washington, 1997.
- PERSONICK, S. D. Receiver design for digital fiber optic communication systems, Part I and II. Bell System Technical Journal, 1973, vol. 52, no. 6, p. 843–886.
- MUOI, T. V. Receiver design for optical-fiber systems. Journal of Lightwave Technology, 1984, vol. 2, no. 3, p. 243–265.
- Perkin Elmer, Silicon Avalanche Photodiodes C30902E, C30902S, C30921E, C30921S. Optoelectronics product data sheet, [online] http://optoelectronics.perkinelmer.com.
- Perkin Elmer, High-Performance Emitters & Detectors for the Most Demanding Applications. [online] http://optoelectronics. perkinelmer.com.
- PROKES, A., ZEMAN, V. Temperature compensation of the responsivity of avalanche photodiodes in free-space optical communication systems. In Proc. IEEE-Siberian Conference on Control and Communications SIBCON-2003. Tomsk (Russia), 2003, p. 102–107.

Keywords: Avalanche photodiode, photodiode gain, excess noise factor, temperature compensation, receiver sensitivity

**V. Otevrel, Z. Raida**
[references] [full-text]

Mean-Adaptive Real-Coding Genetic Algorithm and its Applications to Electromagnetic Optimization (Part One)

In the paper, a novel instance of the real-coding steady-state genetic algorithm, called the Mean-adaptive real-coding genetic algorithm, is put forward. In this instance, three novel implementations of evolution operators are incorporated. Those are a recombination and two mutation operators. All of the evolution operators are designed with the aim of possessing a big explorative power. Moreover, one of the mutation operators exhibits self-adaptive behavior and the other exhibits adaptive behavior, thereby allowing the algorithm to self-control its own mutability as the search advances. This algorithm also takes advantage of population-elitist selection, acting as a replacement policy, being adopted from evolution strategies.

The purpose of this paper (i.e., the first part) is to provide theoretical foundations of a robust and advanced instance of the real-coding genetic algorithm having the big potential of being successfully applied to electromagnetic optimization.

- BACK, T., SCHWEFEL, H. P. An overview of evolutionary algorithms for parameter optimization. Evolutionary Computation Journal. The MIT Press, 1993, vol. 1, no. 1, p. 1–23.
- BEYER, H. G., DEB, K. On self-adaptive features in real-parameter evolutionary algorithms. IEEE Transactions on Evolutionary Computation, 2001, vol. 5, no. 3, p. 250–270.
- HANSEN, N., OSTERMEIER, A. Completely derandomized selfadaptation in evolution strategies. Evolutionary Computation RADIOENGINEERING, VOL. 16, NO. 3, SEPTEMBER 2007 29 Journal. The MIT Press, 2001, vol. 9, no. 2, pp. 159 - 195.
- HERRERA, F., LOZANO, M., SANCHEZ, A. M. A taxonomy for the crossover operator for real-coded genetic algorithms: An experimental study. International Journal of Intelligent Systems. Wiley Periodicals, Inc., 2003, vol. 18, no. 3, p. 309–338.
- LOZANO, M., HERRERA, F., CANO, J. R. Replacement strategies to preserve useful diversity in steady-state genetic algorithms. Information Sciences, in press (2006).
- LOZANO, M., HERRERA, F., CANO, J. R. Replacement strategies to maintain useful diversity in steady-state genetic algorithms. In Proceedings of the 8th Online World Conference on Soft Computing in Industrial Applications, September 2003.
- OTEVREL, V., OLIVA, L. Comparison of real-coding genetic algorithm with particle swarm optimization on the bandgap bandwidth maximization problem. In Proceedings of the 17th International Conference Radioelektronika 2007. Brno: Brno University of Technology, 2007, p. 655–658.
- OTEVREL, V., RAIDA, Z. Wide band global optimization of microstrip line using novel polytope and real genetic algorithms. In Proceedings of the Int. Conference on Electromagnetics in Advanced Applications ICEAA'03. Polytecnico di Torino, 2003, p. 131–134.
- PERIAUX, J., WINTER, G. (editors) Genetic Algorithms in Engineering and Computer Science. John Wiley & Sons Inc., 1995.
- SURRY, P. D. A Prescriptive Formalism for Constructing Domain- Specific Evolutionary Algorithms. Dissertation thesis. University of Edinburg, 1998.
- VINCENT, J. Numerical Optimization using Genetic Algorithms. Technical Report (available from http://dec.bournemouth.ac.uk/staff/ jvincent/ec/numerical_optimisation_using_genetic_algorithms.pdf). University of Bournemouth, UK, 2003.

Keywords: Real-coding genetic optimization, Mean-adaptive real-coding genetic algorithm, mean-adaptive mutation, Gaussian mutation with adaptive step size control, uniform-wise crossover, population-elitist selection

**V. Otevrel, Z. Raida**
[references] [full-text]

Mean-Adaptive Real-Coding Genetic Algorithm and its Applications to Electromagnetic Optimization (Part Two)

In the paper, a novel instance of the real-coding genetic algorithm (RCGA), called the Mean-adaptive real-coding genetic algorithm (MAD-RCGA), is applied along with other RCGAs, to selected problems in microwaves. The problems include the design of a microstrip dipole, the design of frequency-selective surfaces, and the design of a Yagi antenna. Apart from other things, the purpose of this paper is to compare these instances with MAD-RCGA on problems having some technical relevance.

- BALLESTER, P. J., CARTER, J. N. An effective real-parameter genetic algorithm with parent centric normal crossover for multimodal optimization. In Proc. of the Genetic and Evolutionary Computation Conference GECCO'04. Springer-Verlag, 2004, p. 901-913.
- BEYER, H. G., DEB, K. On self-adaptive features in real-parameter evolutionary algorithms. IEEE Tran. on Evolutionary Computation, 2001, vol. 5, no. 3, p. 250-270.
- CERNOHORSKY, D., RAIDA, Z., SKVOR, Z., NOVACEK, Z. Analysis and Optimization of Microwave Structures. Brno: VUTIUM Publishing, 1999. (In Czech).
- DEB, K., JOSHI, D., ANAND, A. Real-Coded Evolutionary Algorithms with Parent-Centric Recombination. KanGAL (Kanpur Genetic Algorithms Laboratory) Technical Report No. 2001003. Indian Institute of Technology Kanpur, 2001.
- DEB, K., ANAND, A., JOSHI, D. A Computationally Efficient Evolutionary Algorithm for Real Parameter Optimization. KanGAL (Kanpur Genetic Algorithms Laboratory) Technical Report No. 2002003. Indian Institute of Technology Kanpur, 2002.
- DEB, K., ANAND, A., JOSHI, D. A computationally efficient evolutionary algorithm for real parameter optimization. Evolutionary Computation Journal. MIT Press, 2002, vol. 10, no. 4, p. 371-395.
- DEB, K. A Population-Based Algorithm Generator for Real Parameter Optimization. KanGAL (Kanpur Genetic Algorithms Lab.) Technical Report No. 2003003. Indian Inst. of Techn. Kanpur, 2003.
- DEB, K. A population-based algorithm generator for real parameter optimization. Soft Computing. Springer-Verlag, 2005, vol. 9, no. 4, p. 236-253.
- HERRERA, F., LOZANO, M. Two-loop real-coded genetic algorithms with adaptive control of mutation step sizes. Applied Intelligence. Kluwer Academic Publishers, 2000, vol. 13, pp. 187-204.
- HERRERA, F., LOZANO, M., SANCHEZ, A. M. A taxonomy for the crossover operator for real-coded genetic algorithms: An experimental study. International Journal of Intelligent Systems. Wiley Periodicals, Inc., 2003, vol. 18, no. 3, p. 309-338.
- LOZANO, M., HERRERA, F., KRASNOGOR, N., MOLINA, D. Real-coded memetic algorithms with crossover hill-climbing. Evolutionary Computation Journal. MIT Press, 2004, vol. 12, p. 273-302.
- MUNK, B. A. Frequency-Selective Surfaces: Theory and Design. Chichester: J. Wiley & Sons, 2000.
- OTEVREL, V., RAIDA, Z. Wide band global optimization of microstrip line using novel polytope and real genetic algorithms. In Proc. of the International Conference on Electromagnetics in Advanced Applications ICEAA'03. Polytecnico di Torino, 2003, p. 131-134
- OTEVREL, V., RAIDA, Z. Mean-adaptive real-coding genetic algorithm and its application to electromagnetic optimization (part one). Radioengineering. 2007, vol. 16, no. 3, p. 19-29.
- SCOTT, C. Spectral-Domain Method in Electromagnetics. Norwood: Artech House, 1989.

Keywords: Mean-adaptive real-coding genetic algorithm, planar dipole, frequency-selective surface, Yagi antenna

**P. Hazdra, M. Mazanek, J. Cermak**
[references] [full-text]

Wideband Rectangular Microstrip Patch Antenna Using L-Probe Feeding System

Paper focuses on so-called L-probe feeding technique suitable for wideband (30% relative bandwidth) driving of microstrip patch antennas. Physical explanation, simulation and measurement are presented. Further modification for improvement of radiation characteristic is also proposed.

- MAK, C. L., LUK, K. M., LEE, K. F., CHOW, Y. L. Experimental study of a microstrip patch antenna with an L-shaped probe. IEEE Trans-AP, 2000, vol. 48, no. 5.
- BAHL, I., BHARTIA, P., GARG, R. Microstrip Antenna Design Handbook. Artech House, 2001.
- www.zeland.com
- MAS, Ch. L., WONG, H., LUK, K. W. High-Gain and Wide-Band Single-Layer Patch Antenna for Wireless Communications. IEEE Trans. on Vehicular Technology, 2005, vol. 54, no. 1.
- www.cst.com
- ZHANG, X-Y., XUE, Q., HU, B-J., XIE, S-L. A Wideband Antenna with Dual Printed L-Probes for Cross-Polarization Suppression. IEEE XPLORE.

Keywords: Microstrip patch antenna, L-probe, wideband antennas, proximity coupling

**Z. Reznicek, Z. Raida**
[references] [full-text]

Quadric Resistive Sheet Profile for Wideband Antennas

A new type of a nonreflecting resistive dipole antenna with quadric continuous resistivity profile is presented in this paper. The antenna is mathematically described and compared with the antenna originally proposed by Wu and King. The verification of a proposed theory and the comparison between Wu-King and quadric profile are carried out by simulation models that were designed for this purpose. The attention is turned to the proper attenuation of a wave excited on the resistive sheet, especially.

- WU, T. T., KING, W. P. The cylindrical antenna with nonreflecting resistive loading. IEEE Transactions on Antennas and Propagation, 1965, vol. 13, no. 3, p. 369-373.
- WRIGHT, D., PREWITT, J. Radiating dipole antenna with tapered impedance loading. IEEE Transactions on Antennas and Propagation, 1975, vol. 23, no. 6, p. 811-814.
- KANDA, M., DRIVER, L. D. An isotropic electric-field probe with tapered resistive dipoles for broad-band use, 100 kHz to 18 GHz. IEEE Transactions on Microwave Theory and Techniques, 1987, vol. 35, no. 2, p. 124-130.
- REZNICEK, Z., RAIDA,Z. Extended theory of Wu-King travelling wave resistive antenna. Elektrorevue, Online. www.elektrorevue.cz
- ESSELLE, K. P.,STUCHLY, S. S., Pulse-receiving characteristics of resistively loaded dipole antennas. IEEE Translations on Antennas and Propagation, 1990, vol. 38, no. 10, p. 1677-1683.

Keywords: UWB antenna, resistive sheet, Wu-King profile, time domain, EMC, geophysical tomography

**A. Magyar, G. Miko, R. Seller**
[references] [full-text]

Combined Calibration Method and its Realization for Direction Finding Antenna Systems with Patch Antennas

A novel radio channel compensation method aiming to give optimal calibration for microstrip antenna array systems is presented in this paper, realized for an actual DOA measurement antenna system using microstrip antennas to sample the electromagnetic field, operating at 4.5GHz. This new approach considers mismatch between antennas and channel RF ports, channel transmission inequalities, and also decreases the effects of multipath propagation components of calibration reference signals by placing the calibration reference signal feeding network on the microstrip antenna array bearer, directly beside the antenna patches. It is combined with orthogonal spread spectrum calibration signal utility for continuous uninterrupted measurements. The spread spectrum calibration signal is orthogonal to the continuous wave (CW) signal to be measured, therefore, the 2 signals can be separated in the receiver, enabling them to be present simultaneously. DOA measurement results are shown, measured with the realized integrated microstrip patch antenna array with calibration network hardware.

- LESHEM, A., WAX, M. Array calibration in the presence of multipath. IEEE Transactions on Signal Processing, 2000, vol. 48, no. 1, p. 53-59.
- DANDEKAR, K.R., LING, H., XU, G. Smart antenna array calibration procedure including amplitude and phase mismatch and mutual coupling effects. In Proceedings of the IEEE International Conference on Personal Wireless Communications, 2000, p. 293 to 297.
- MIKO, GY., MAGYAR, A., SELLER, R. Adaptive radio direction finding measurement results and the aspects of measurements, investigated with a re-configurable, 16-channel radio direction finder antenna array. In Proceedings of the 7th COST 284 Workshop, Chexbres (Switzerland), 2005.
- VOLGYI, F. High-gain microstrip antennas. Hiradastechnika, vol. XXXVI, no. 6, p. 266-281.
- LINEBARGER, D. A., JOHNSON, D. H. The effect of spatial averaging on spatial correlation matrices in the presence of coherent signals. IEEE Transactions on Acoustics, Speech and Signal Processing, 1990, vol. 38, no. 5, p. 880-884.

Keywords: Microstrip patch antennas, smart antenna systems, processing channel calibration, spread spectrum, Direction of Arrival (DOA)

**N. Majurec, D. Bonefacic**
[references] [full-text]

Analysis and Implementation of Polarization Schemes for Polarimetric Radar Systems

Polarization schemes recently employed in atmospheric radar systems are described and compared. The considered polarization schemes are: the switching polarization scheme, the hybrid polarization scheme, and the extended hybrid polarization scheme. Performance of polarimetric radar systems using each of these schemes is simulated. These simulations provide insight into strengths and weaknesses of each scheme, and as such, provide a way of choosing the right one for a particular radar application. Results show that the widely accepted hybrid polarization scheme suffers from significant mutual coupling of the measurable values. Depending on the application, the switching or extended hybrid scheme proves to be better choice.

- DOVIAK, R. J., ZRNIC, D. S. Doppler Radar and Weather Observations. San Diego (California): Academic Press, 1984.
- BRINGI, V. N., CHANDRASEKAR, V. Polarimetric Doppler Weather Radar: Principles and Applications. New York: Cambridge University Press, 2001.
- MAJUREC, N., SEKELSKY, S. M. SCHAUBERT, D. H., HONG, Y., RUTLEDGE, S. A., STEPHENS, G. L., HEYMSFIELD, A. Triple-frequency radar for cloud and precipitation microphysics research. In Proc. of the 19th Int. Conf. on Applied Electromagnetics and Communications (ICECom 2003). Dubrovnik (Croatia), 2003, p. 18-21.
- MATROSOV, S. Y., REINKING, R. F., KROPFLI, R. A., MARTNER, B. E., BARTRAM, B. W. On the use of radar depolarization ratios for estimating shapes of ice hydrometeors in winter clouds. J. of Applied Meteorology, 2001, vol. 40, p. 479-490.
- MATROSOV, S. Y. Theoretical study of radar polarization parameters obtained from cirrus clouds. Journal of Atmospheric Sciences, 1991, vol. 48, p. 1062-1070.
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- ZRNIC, D. Simultaneous Differential Polymetric Measurements and Co-Polar Correlation Coefficient Measurement. United States Patent, March 1996. Patent No. 5,500,646.
- MATROSOV, S. Y. Depolarization Estimates from Linear H and V Measurements with Weather Radars Operating in Simultaneous Transmission-Simultaneous Receiving Mode. Cooperative Inst. for Research in the Environmental Sciences, Univ. of Colorado, NOAA-Environmental Technology Laboratory, Boulder, Colorado, 2003.

Keywords: Weather radar, polarimetric radar, switching polarization scheme, hybrid polarization scheme, extended hybrid polarization scheme

**D. Bonefacic, J. Jancula, N. Majurec**
[references] [full-text]

Model of a Monopulse Radar Tracking System for Student Laboratory

Development, construction and testing of a student laboratory model of the radar system that can be used for monopulse tracking is described. The laboratory model is simple and can be assembled from the existing equipment while the missing parts can be manufactured in a basically equipped RF electronics workshop. The laboratory model is used for student laboratory exercises as a part of a basic course on radar systems. The system is based on a Σ-Δ hybrid for processing signals obtained from two antennas. The composition of the model is described. Student exercises and measurements on the model are proposed. Alternative instruments which can be used in the model are considered. Possible improvements of the model are discussed.

- SKOLNIK, M. I. Introduction to Radar Systems. 3rd ed. New York: McGraw-Hill, 2001.
- LEONOV, A. I., FORMICHEV, K. I. Monopulse Radar. Norwood: Artech House, 1986.
- POZAR, D. M., Microwave Engineering. Reading: Addison-Wesley, 1993.
- BARTOLIC, J. Microwave Electronics - Lecture Notes (in Croatian). http://www.rc.fer.hr/nastava/me/predavanja.asp
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Keywords: Education, radar, monopulse radar, tracking

**V. Sadek**
[references] [full-text]

The Conformal Correction in the Strip Centered Coaxial Line Analysis

The presented work reports on the novel analysis of the strip-centered coaxial line. The conformal mapping method is used.

For a narrow central strip a very easy conformal mapping is described that maps this structure onto the rectangular model line, but great distortion for wide strip inhibits application of this mapping in all the extent. The conformal mapping method allows to correct this fault very smartly by extension in auxiliary plane.

Two different numerical models are also mentioned as comparative solutions of strip-centered coaxial line analysis. One of them is based on numerical evaluating of the Schwarz Christoffel integral, the other (in two modifications) is based on boundary element method (BEM).

- SVACINA, J. Electromagnetic Compatibility - lectures. Textbook of the Brno University of Technology, FEKT VUT Brno, 2002.
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Keywords: Strip-centered coaxial line, characteristic impedance, conformal mapping, conformal correction, numerical solution of Schwarz-Christoffel integral, BEM

**Z. Ruzicka, S. Hanus**
[references] [full-text]

UMTS Network Model for Interference Analysis - Optimization of Spreading Codes Order

This article deals with mathematical modeling of UMTS network. The presented model is designed for interference analysis in this network. The paper presents the set of simulations based on an idea of a specific order of Walsh codes.

In the first part the mathematical model is presented. This model is designed for Matlab and is based on 3GPP specifications. The second part describes the method of specific ordering of Walsh spreading codes. The specific order can decrease the interference level in the radio network of UMTS which is caused by multipath propagation. The simulation results are presented, too.

- KORHONEN, J. Introduction to 3G Mobile Communications. Norwood: Artech House, 2001.
- 3GPP Technical Specification Group Radio Access Network - Spreading and Modulation (FDD); TS 25.213 V6.3.0 [online], available at http://www.3gpp.org, 2005.
- 3GPP Technical Specification Group Radio Access Network - Physical Layer, General Description; TS 25.201 V6.2.0 [online], available at http://www.3gpp.org, 2005.
- BOSTELMANN, G., ZARITS, R. UMTS Design Details & System Engineering. Karlsruhe: INACON GmbH, 2002.
- WIESER, V., PSENAK, V. Hybrid adaptation simulator for next generation of mobile communication networks. In 6th International Conference on Research in Telecommunication Technology - RTT 2005. Hradec n/Moravici (Czech Republic), 2005.
- WIESER, V., PSENAK, V. Data rate increasing for high speed multimedia services in enhanced WCDMA mobile radio network. In IWSSIP 2006, 13th International Conference on Systems, Signals and Image Processing. Budapest (Hungary), 2006, p. 75-78.

Keywords: UMTS, orthogonal codes, optimization

**I. Baronak, M. Halas**
[references] [full-text]

Mathematical Representation of VoIP Connection Delay

The main topic of this article is to define mathematical formulation of VoIP connection delay model. It handles about all partial delay components, the mechanism of their generation, facilities and their mathematical formulation. Thereafter based on mathematical formulation of all partial delay components, the final mathematical model of whole VoIP call delay is created. In conclusion of this article the results of the designed mathematical model are compared with the experimentally gained results.

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Keywords: VoIP, delay, mathematical model, M/D/1/∞

**I. M. B. Nogales**
[references] [full-text]

Routing Protocol for Mobile Ad-hoc Wireless Networks

Bluetooth is a cutting-edge technology used for implementing wireless ad hoc networks. In order to provide an overall scheme for mobile ad hoc networks, this paper deals with scatternet topology formation and routing algorithm to form larger ad hoc wireless Networks. Scatternet topology starts by forming a robust network, which is less susceptible to the problems posed by node mobility. Mobile topology relies on the presence of free nodes that create multiple connections with the network and on their subsequently rejoining the network. Our routing protocol is a proactive routing protocol, which is tailor made for the Bluetooth ad hoc network. The connection establishment connects nodes in a structure that simplifies packet routing and scheduling. The design allows nodes to arrive and leave arbitrarily, incrementally building the topology and healing partitions when they occur. We present simulation results that show that the algorithm presents low formation latency and also generates an efficient topology for forwarding packets along ad-hoc wireless networks.

- Bluetooth SIG, Specification of the Bluetooth system, Core, Version 1.1. Bluetooth SIG Homepage: www.bluetooth.com.
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Keywords: Bluetooth, mobile ad-hoc wireless networks, routing algorithm and performance

**O. Hala**
[references] [full-text]

Software for CATV Design and Frequency Plan Optimization

The paper deals with the structure of a software medium used for design and sub-optimization of frequency plan in CATV networks, their description and design method. The software performance is described and a simple design example of energy balance of a simplified CATV network is given. The software was created in programming environment called Delphi and local optimization was made in Matlab.

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Keywords: CATV, CSO, CTB, software, optimization, ACO, Cable Television, Net, styles

**T. Dostal, V. Axman**
[references] [full-text]

Biquads Based on Single Negative Impedance Converter Implemented by Classical Current Conveyor

The paper deals with continuous-time ARC biquadratic (second-order) filters based on the single classical three-port current conveyors, so called second generation CC II. A unique application of the CC II is discussed, when the terminals Y and Z are connected together. Using this way a negative impedance converter is obtained as a suitable building block in synthesis of several biquads, including notch filters.

- SEDRA, A. S., SMITH, K. C. A second generation current conveyor and its applications. IEEE Transaction on Circuit Theory, vol. CT-17, Feb. 1970, p. 132-134.
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Keywords: Analogue circuits, active RC filters, biquads, current conveyors, negative impedance converters

**L. Docheva, A. Bekiarski, I. Dochev**
[references] [full-text]

Analysis of Analog Neural Network Model with CMOS Multipliers

The analog neural networks have some very useful advantages in comparison with digital neural network, but recent implementation of discrete elements gives not the possibility for realizing completely these advantages. The reason of this is the great variations of discrete semiconductors characteristics.

The VLSI implementation of neural network algorithm is a new direction of analog neural network developments and applications. Analog design can be very difficult because of need to compensate the variations in manufacturing, in temperature, etc. It is necessary to study the characteristics and effectiveness of this implementation. In this article the parameter variation influence over analog neural network behavior has been investigated.

- LEHMAN, T. Hardware Learning in Analog VLSI Neural Networks. Ph.D. thesis, Technical University of Denmark, 1994.
- MOERLAND, P., FIESLER E. Neural Network Adaptations to hardware implementation. IDIAP'97, 1997.
- DRAGHICI, S. Neural Network in analog hardware-design and implementation issues. Int. J. of Neural Systems, 2000, vol.10, no. 1, pp. 19-42.
- MADRENAS, J., COSP, J., LUCAS, O., ALARCON, E., VIDAL, E., VILLAR, G. BIOSEG: A Bioinspired VLSI Analog System for Image Segmentation. In ESANN'2004 proceedings - European Symposium on Artificial Neural Networks. 2004, pp. 411-416.
- FIERES, J., GRUBL, A., PHILIPP, S., MEIER, K., SCHEMMEL, J., SCHURMANN, F. A Platform for Parallel Operation of VLSI Neural Networks. BICS 2004, 2004.
- BEKIARSKI, A., DOCHEVA, L. Influence of the type of analog neural network initialisation. E&E. 2007 (to be published).
- LANSNER, J. Analogue VLSI Implementation of Artificial Neural Networks. Ph.D. thesis, Technical University of Denmark, 1994.

Keywords: Analog neural networks, VLSI, robotic

**V. Sebesta**
[references] [full-text]

Spreading Sequences Generated Using Asymmetrical Integer-Number Maps

Chaotic sequences produced by piecewise linear maps can be transformed to binary sequences. The binary sequences are optimal for the asynchronous DS/CDMA systems in case of certain shapes of the maps. This paper is devoted to the one-to-one integer-number maps derived from the suitable asymmetrical piecewise linear maps. Such maps give periodic integer-number sequences, which can be transformed to the binary sequences. The binary sequences produced via proposed modified integer-number maps are perfectly balanced and embody good autocorrelation and crosscorrelation properties. The number of different binary sequences is sizable. The sequences are suitable as spreading sequences in DS/CDMA systems.

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Keywords: Chaotic map, integer-number map, binary spreading sequence

**A. Boudabous, L. Khriji, A. B. Atitallah, P. Kadionik, N. Masmoudi**
[references] [full-text]

Efficient Architecture and Implementation of Vector Median Filter in Co-Design Context

This work presents an efficient fast parallel architecture of the Vector Median Filter (VMF) using combined hardware/software (HW/SW) implementation. The hardware part of the system is implemented using VHDL language, whereas the software part is developed using C/C++ language. The software part of the embedded system uses the NIOS-II softcore processor and the operating system used is μClinux.

The comparison between the software and HW/SW solutions shows that adding a hardware part in the design attempts to speed up the filtering process compared to the software solution. This efficient embedded system implementation can perform well in several image processing applications.

- ATITALLAH, A.B., KADIONIK, P., GHOZZI, F., NOUEL, P., MASMOUDI, N., LEVI, H., An FPGA implementation of HW/SW codesign architecture for H.263 video coding. AEU - International Journal of Electronics and Communications, Dec 2006.
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- Nios-II Development Kit, STRATIX Edition, ALTERA 2006, http://www.altera.com/products/devkits/altera/kitniosii 2S30.html.
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Keywords: Color image, FPGA, SoPC, NIOS-II, VMF

**M. Drutarovsky, P. Galajda**
[references] [full-text]

A Robust Chaos-Based True Random Number Generator Embedded in Reconfigurable Switched-Capacitor Hardware

This paper presents a new chaos-based True Random Number Generator (TRNG) with a decreased voltage supply sensitivity. Contrary to the traditionally used sources of randomness it uses a well-defined deterministic switched-capacitor circuit that exhibits chaos. The whole design is embedded into a commercially available mixed-signal Cypress PSoC reconfigurable device without any external components. The proposed design is optimized for a reduction of influence of the supply voltage to the quality of the generated random bit stream. The influence of circuit non-idealities is significantly reduced by the proposed XOR corrector and optimized circuit topology. The ultimate output bit rate of the proposed TRNG is 60 kbit/s and the quality of generated bit-streams is confirmed by passing standard FIPS and correlation statistical tests performed in the full range of PSoC device supply voltages.

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Keywords: Cryptography, chaos, Markov chains, TRNG, PSoC mixed-signal hardware, FIPS tests

**J. Dzubera**
[references] [full-text]

Examination of Newton\'s Method Used for Indirect Frequency Offset Estimation

This paper deals with the topic of an indirect carrier frequency offset estimation and elimination. The main goal is to modify a conventional method as an attempt to develop a different approach and then to compare the performance of the modified method with the performance of the conventional one. The conventional approach is here represented by the gradient optimization method called the steepest descent. It is the base for the modification which utilizes Newton\'s method for the indirect carrier offset estimation. Both algorithms are implemented as phase-locked loops in a model of communication system. The simulation is processed in Matlab.

- TRANTER, W. H., SHANMUGAN, K. S., RAPPAPORT, T. S., KOSBAR, K. L. Principles of Communication System Simulations with Wireless Applications. 1st ed, New Jersey: Prentice Hall, 2004.
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- DZUBERA, J. The steepest descent and Newton's method used for indirect frequency estimation. In RADIOELEKTRONIKA 2006 - Conference Proceedings. RADIOELEKTRONIKA 2006. Bratislava (Slovakia), 2006, pp. 226 - 229, ISBN 80-227-2388-6.
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Keywords: Carrier frequency recovery, carrier frequency offset estimation, carrier frequency offset elimination, carrier synchronization, Newton’s method, optimization, phase-locked loop, PLL, steepest descent

**P. Bandzi, M. Oravec, J. Pavlovicova**
[references] [full-text]

New Statistics for Texture Classification Based on Gabor Filters

The paper introduces a new method of texture segmentation efficiency evaluation. One of the well known texture segmentation methods is based on Gabor filters because of their orientation and spatial frequency character. Several statistics are used to extract more information from results obtained by Gabor filtering. Big amount of input parameters causes a wide set of results which need to be evaluated. The evaluation method is based on the normal distributions Gaussian curves intersection assessment and provides a new point of view to the segmentation method selection.

- CONG, L., SHA, Y., HOU, B., JIAO, L. Unsupervised image segmentation based on the anisotropic texture information. In The 3rd Int. Conf. on Image and Graphics (ICIG '04). 2004. pp. 124-127.
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- IDRISSA, M., ACHEROY, M. Texture classification using Gabor filters. Pattern Recognition Letters, 2002, vol. 23. no. 9. pp. 1095-1102.
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- GRIGORESCU, S. E., PETKOV, N., KRUIZINGA, P. Comparison of texture features based on Gabor filters. IEEE Transactions on Image Processing, 2002, vol. 11, no. 10, pp. 1160-1167.

Keywords: Texture segmentation, image segmentation, Gabor filters, efficiency evaluation

**M. Paralic, R. Jarina**
[references] [full-text]

Iterative Unsupervised GMM Training for Speaker Indexing

The paper addresses a novel algorithm for speaker searching and indexation based on unsupervised GMM training. The proposed method doesn\'t require a predefined set of generic background models, and the GMM speaker models are trained only from test samples. The constrain of the method is that the number of the speakers has to be known in advance. The results of initial experiments show that the proposed training method enables to create precise GMM speaker models from only a small amount of training data.

- ADAMI, A. G., KAJERAK, S. S., HERMANSKY, H. A new speaker change detection method for two-speaker segmentation. In Proc. ICASSP-2002. Orlando (Florida, USA), May 2002.
- AKITA, Y., KAWAHARA, T. Unsupervised speaker indexing using anchor models and automatic transcription of discussions. In Proc. of Eurospeech 2003. Geneva (Switzerland), 2003.
- DELACOURT, P., WELLEKENS, CH. J. DISTBIC: A speaker-based segmentation for audio data indexing. Speech Communication, 2000, no. 32 , p. 111 - 126.
- DUNN, R. B., REYNOLDS, D. A., QUATIERI, T. F. Approaches to speaker detection and tracking in conversational speech. Digital Signal Processing, 2000, no. 10, pp. 93-112.
- KWON, S., NARAYANAN, S. A method for on-line speaker indexing using generic reference models. In Proc. of Eurospeech 2003, Geneva (Switzerland), 2003.
- ROSENBERG, A., GORIN, A., PARTHASARATHY, S. Unsupervised speaker segmentation of telephone conversations. In Int. Conf. on Spoken Language Processing, vol. 1, 2002.
- RUSKO, M., DARZAGIN, S., TRNKA, M. SpeechDat - E" telephone speech database as an important source for basic acoustic - phonetic research in Slovak. In ICA 2004: part I. [electronic source], 2004, pp. 1676-1682.
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- STURIM, D. E., REYNOLDS, D. A., SINGER, E., CAMPBELL, J. P. Speaker indexing in large audio databases using anchor models. In Proc. ICASSP, p. 429-432, 2001.
- TRITSCHLER, A., GOPINATH, R. Improved speaker segmentation and segment clustering using the Bayesian Information Criterion. In Proc. EUROSPEECH'99. Budapest (Hungary), September 1999.
- WANG, Y., LIU, Z., HUANG, J.-CH. Multimedia content analysis using both audio and visual clues. IEEE Signal Processing Magazine, November 2000.
- ZHANG, T., KUO, C. C. J. Audio content analysis for online audiovisual data segmentation and classification. IEEE Transactions on Speech and Audio Processing, 2001, vol. 9, no. 4, pp. 441 - 457.

Keywords: Speaker indexing, training, iteration, log. likelihood, Gaussian Mixture Model (GMM)