# June 2004, Volume 13, Number 2

**V. Kvicera, M. Grabner, M. Hlavaty**
[references] [full-text]

Rain Intensity Statistical Processing and Comparison with ITU-R
Recommendations

Rain intensities have been measured since February 1992 by means of a heated siphon raingauge. Rain intensity data gathered over 11-year period were statistically processed, cumulative distributions of rain intensities obtained, and relations between them were compared with ITU-R recommendations.

- Rec. ITU-R P.837-3 Characteristics of precipitation for propagation modelling. ITU, Geneva, March 2003.
- Rec. ITU-R P. 841-2 Conversion of annual statistics to worst-month statistics. ITU, Geneva, March 2003.

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

Modeling Broadband Microwave Structures by Artificial Neural Networks

The paper describes the exploitation of feed-forward neural networks and recurrent neural networks for replacing full-wave numerical models of microwave structures in complex microwave design tools. Building a neural model, attention is turned to the modeling accuracy and to the efficiency of building a model. Dealing with the accuracy, we describe a method of increasing it by successive completing a training set. Neural models are mutually compared in order to highlight their advantages and disadvantages. As a reference model for comparisons, approximations based on standard cubic splines are used. Neural models are used to replace both the time-domain numeric models and the frequency-domain ones.

- RAO, S. Time domain electromagnetics. San Diego: Academic Press, 1999.
- RAIDA, Z. et al. Analyza mikrovlnnych struktur v casove oblasti (Time-domain analysis of microwave structures). Brno: VUTIUM Publishing, 2003.
- CERNOHORSKY, D., RAIDA, Z., SKVOR, Z., NOVACEK, Z. Analyza a optimalizace mikrovlnnych struktur (Analysis and optimization of microwave structures). Brno: VUTIUM Publishing, 1999.
- HAYKIN, S. Neural networks: A comprehensive foundation. Englewood Cliffs: Macmillan Publishing Company, 1994.
- CICHOCKI, A., UNBEHAUEN, R. Neural networks for optimiza-tion and signal processing. Chichester: J. Wiley & Sons, 1994.
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- LEE, J. F. Finite element analysis of lossy dielectric waveguides. IEEE Transactions on Microwave Theory and Techniques. 1994, vol. 42, no. 6, p. 1025 - 1031.
- RAIDA, Z. Modeling EM structures in Neural network toolbox of Matlab. IEEE Antennas and Propagation Magazine. 2002, vol. 44, no. 6, p. 46 - 67.
- DEMUTH, H., BEALE, M. Neural network toolbox for use with Matlab: User's guide. Version 4. Natick: The MathWorks Inc., 2000.
- DE BOOR, C. A Practical guide to splines. Berlin: Springer-Verlag, 1978.
- HARRINGTON, R. F. Field computation by moment methods. 2nd edition. Piscataway: IEEE Press, 1993.
- RAIDA, Z. Broadband design of planar transmission lines: feed-forward neural approach versus recurrent one. In Proceedings of the In-ternational Conference on Electromagnetics in Advanced Applica-tions ICEAA 2003. Torino (Italy), 2003, p. 155 - 158.
- LUKES, Z., RAIDA, Z. Design of microwave antennas: neural network approach to time domain modeling of V-Dipole. In Proceedings of the International Conference on Electromagnetics in Ad-vanced Applications ICEAA 03. Torino (Italy), 2003, p. 7 - 10.
- RAIDA, Z. Wideband neural modeling of wire antennas: feed-forward neural networks versus recurrent ones. In Proceedings of the Progress in Electromagnetics Research Symposium PIERS 2003. Honolulu (Hawaii), 2003, p. 717 - 717.

**R. Tkadlec**
[references] [full-text]

S-Parameter Measurements in the Time Domain

The paper provides a basic overview of the theory of time-domain measurements. Results of the use time-domain techniques to obtain S-parameter are here presented. Advantages and disadvantages of this technique compared to frequency-domain measurements are mentioned.

- DE JONGH, R. V., HAJIAN, M., LIGTHART, L. P. Antenna time-domain measurement techniques. IEEE Transactions on Antennas and Propagation. 1997, vol. 39, no.5, p. 7 - 11.
- NICOLSON, A. M., ROSS, G. F. Measurement of the intrinsic pro-perties of materials by time-domain techniques. IEEE Transactions on Instrumentation and Measurement. 1970, vol. 19, no.11, p. 377 to 382.
- CERNOHORSKY, D., NOVACEK, Z., RAIDA, Z. Electromagnetic Waves and Transmission Lines. 2nd edition. Brno: VUTIUM Publishing, 1999. ISBN 80-214-1261-5.

**V. Stofanik, I. Balaz**
[references] [full-text]

Frequency Stability Improvement in Direct Digital Frequency Synthesis

The paper describes a digital frequency synthesizer that incorporates a novel method of the clock signal frequency versus temperature dependency compensation. The clock signal is derived directly from a dual mode crystal oscillator (DMXO). With introducing the method, synthesized signal frequency versus temperature instability below a0.15ppm can be obtained over a wide temperature range (between 45°C and +85°C). Since a temperature information is obtained directly from a crystal itself rather than from an external sensor, temperature offset and lag effects are eliminated.

- SCHODOWSKI, S. S. Resonator self-temperature-sensing using a dual-harmonic-mode oscillator. In Proceedings of the 43rd Annual Symposium on Frequency Control. 1989, p. 2 - 7.
- FILLER, R. L., VIG, J. R. Resonators for the microcomputer compensated crystal oscillator. In Proceedings of the 43rd Annual Sym-posium on Frequency Control. 1989, p. 8 - 15.
- BENJAMINSON, A., STALLINGS, S. C., A Microcomputer com-pensated crystal oscillator using a dual-mode resonator. In Proc. of the 43rd Annual Symposium on Frequency Control. 1989, p. 20-26.
- JACKSON, E., PHILLIPS, H., ROSE, B. E., The microcomputer compensated crystal oscillator - a progress report. In Proceedings of the 1996 IEEE International Frequency Control Symposium. 1996, p. 687 - 692.
- STOFANIK, V., BALAZ, I., MINARIK, M. Temperature-compensated frequency synthesizer. In Proceedings of the 2001 International Symposium on Signals, Systems, and Electronics ISSSE. Tokyo (Japan), 2001, p. 432 - 435.
- STOFANIK, V., BALAZ, I., MINARIK, M. Digitally temperature-compensated DDS. In Proc. of the 2001 IEEE/EIA International Frequency Control Symposium, Seattle, USA, 2001, p. 816 - 819.
- KROUPA, V. F. Phase and amplitude disturbances in direct digital frequency synthesizers. In Transactions on Ultrasonics, Ferroelectrics, and Frequency Control. 1999, vol. 46, no. 3, p. 481 - 486.
- KROUPA, V. F., Close to the carrier noise in DDS. In Proceedings of the 1996 IEEE International Frequency Control Symposium. Honolulu (USA), 1996, p. 934 - 941.

**J. Petrzela, V. Pospisil**
[references] [full-text]

Nonlinear Resistor with Polynomial AV Characteristics and Its
Application in Chaotic Oscillator

This paper shows the realization of two terminal devices with an arbitrary polynomial nonlinearity up to the fifth order. The proposed design procedure is completely systematic using minimum of components. The very heart of our conception is four-channel four-quadrant analog multiplier MLT04. The implementation of synthesized nonlinear resistor as a general nonlinearity in chaotic oscillator is also presented and experimentally verified.

- PETRZELA, J. Obvodova realizace konzervativniho chaotickeho oscilatoru. Elektrorevue. 2004.
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- ITOH, M. Synthesis of electronic circuits for simulating nonlinear dynamics. International Journal of Bifurcation and Chaos. 2001, vol. 11, no. 3, p. 605 - 653.
- ZHONG, G. Q., KO, K. T., MAN, K. F., TANG, K. S. A systematic procedure for synthesizing two terminal devices with polynomial nonlinearity. International Journal of Circuit Theory and Applications. 2001, vol. 29, p. 241 - 249.
- SPROTT, J. C., LINZ, S. J. Algebraically simple chaotic flows. International Journal of Chaos Theory and Applications, 2000, vol. 5, no. 2, p. 1 - 20.
- POSPISIL, J., KOLKA, Z., HORSKA, J., BRZOBOHATY, J. Simplest ODE equivalents of Chua's equations. International Journal of Bifurcation and Chaos. 2000, vol. 10, no. 1, p. 1 - 23.
- LAYOS, M.C., HARITANTIS, I. On the derivation of current-mode floating inductors. International Journal of Circuit Theory and Applications. 1997, vol. 25, p. 29 - 36.
- ELWAKIL, A. S., KENNEDY, M. P. Inductorless hyperchaos generator. Microelectronics Journal. 1999, vol. 30, p. 739 - 743.
- ELWAKIL, A. S., KENNEDY, M. P. Generic RC realizations of Chua's circuit. International Journal of Bifurcation and Chaos. 2000, vol. 10, no. 8, p. 1981 - 1985.
- ELWAKIL, A. S., KENNEDY, M. P. Chaotic oscillator configuration using a frequency dependent negative resistor. Journal of Circuits, Systems and Computers. 1999, vol. 9, no. 3 - 4, p. 229 - 242.
- ZHONG, G. Q., TANG, W. Circuitry implementation and synchronization of Chen's attractor. International Journal of Bifurcation and Chaos. 2002, vol. 12, no. 6, p. 1423 - 1427.
- NDJOUNTCHE, T., UNBEHAUEN, R., LUO, F. Electronically tunable generalized impedance converters structures. International Journal of Circuit Theory and Applications. 1999, vol. 27, p. 517 - 522.
- YANG, X., LI, Q., CHEN, G. A twin-star hyperchaotic attractor and its circuit implementation. International Journal of Circuit Theory and Applications. 2003, vol. 31, p. 637 - 640.
- ZHONG, G. Q., MAN, K. F., CHEN, G. A systematic approach to generating n-scroll attractors. International Journal of Bifurcation and Chaos. 2002, vol. 12, no. 12, p. 2907 - 2915.
- PETRZELA, J. On the class of chaos generators with single quadratic nonlinearity. In Proceedings of the 14th Czech-Slovak Scientific Conference. Bratislava (Slovakia), 2004, p. 5 - 9.
- BAI, E., LONNGREN, K. E., SPROTT, J. C. On the synchronization of a class of electronic circuits that exhibit chaos. Chaos, Solitons and Fractals. 2002, vol. 13, p. 1515 - 1521.
- ELWAKIL, A. S., SOLIMAN, A. M. Current conveyor chaos generators. IEEE transactions on CAS-I: Fundamental Theory and Applications. 1999, vol. 46, no. 3, p. 393 - 398.

**Z. Peric, S. Bogosavljevic**
[references] [full-text]

Asymptotic Analysis of Optimal Piecewise Uniform Polar Quantization

In this paper, a simple and complete asymptotical analysis is given for a mean square error (MSE) piecewise uniform polar quantizer (PUPQ). We show that PUPQ has the same performance as the asymptotic nonuniform polar quantizer (NPQ) and has implementation complexity between complexities of NPQ and uniform polar quantization. The goal of this paper is solving the quantization problem in case of PUPQ and finding the corresponding support region.

- ARSLAN, F. T. Adaptive Bit Rate Allocation in Compression of SAR Images with JPEG2000. University of Arizona, 2001.
- PERIC, Z. H., JOVKOVIC, J. Application of the optimal uniform polar quantization on complex reflectivity function. Advances in Electrical and Computer Engineering. 2002, vol. 9, no. 1, p. 80 - 86.
- PERIC, Z. H., STEFANOVIC, M. Asymptotic analysis of optimal uniform polar quantization. International Journal of Electronics and Communications. 2002, vol. 56, no. 5, p. 345 - 347.
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- NA, S., NEUHOFF, D. L. On the support of MSE-optimal, fixed-rate scalar quantizers. IEEE Transactions of Information Technology. 2001, vol. 47, no. 7, p. 2972 - 2982.
- PERIC, Z. H. Piecewise uniform product two-dimensional Laplace source quantization. Electronics and Electrical Engineering. 2003, vol. 44, no. 2, p. 13 - 17.
- POPAT, K., ZEGER, K. Robust quantization of memoryless sources using dispersive FIR filters. IEEE Transactions on Communication. 1992, vol. 40, no. 11, p. 1670 - 1674.

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

Reduction of Elastomagnetic Sensor Errors by Using Neural Networks

This article deals with possibilities of reduction of elastomagnetic sensor errors. Elastomagnetic sensors are used for measuring of massive pressure force (of range about 200 kN). At the same time with demands on sensor accuracy, a filter can be added to the measuring set. The function of this filter is to regulate the basic metrological characteristics of sensor in order to achieve the smallest deviation from an ideal transfer characteristic. The using of exactly defined algorithm of reducing sensor errors is not appropriate in this case. So, the unconventional solution is using of the neural networks.

- MOJZIS, M. et al. Properties of 200 kN force sensor. Journal of Electrical Engineering. 1999, vol. 50, no 3 - 4, p. 105 - 108.
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- KOVAC, D. The feeding and evaluating circuits for an elasto-magnetic sensor. Journal of Electrical Engineering.1999, vol. 50, no 7 - 8, p. 255 - 256.
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- HAYKIN, S. Neural Networks (A Comprehensive Foundation). Macmillan College Publishing Company Inc. ISBN 0-02-352761-7, 1994.
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- IEC 61298-2, Process measurement and control devices - General methods and procedures for evaluating performance - Part 2: Tests under reference conditions, 1995-07.
- IEC 60770, Transmitters for use in industrial-process control systems - Part 1: Methods for performance evaluation, 1999-02. Part 2: Methods for inspection and routine testing. Part 2: Methods for inspection and routine testing, 2003-01.
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**B. Taha-Ahmed, M. Calvo-Ramon, L. de Haro-Ariet**
[references] [full-text]

On the High Altitude Platform (HAP) W-CDMA System Capacity

The performance of a downlink power control model, based on a n-th power distance law, is evaluated for high altitude platform station (HAPS) W-CDMA systems. The downlink capacity using this model is compared with the uplink capacity. It is shown that the uplink capacity is higher than the downlink capacity.

- DJUNNIC, G. M., FREDENFELDS, J. Establishing wireless communications services via high-altitude aeronautical platforms: a con-cept whose time has come? IEEE Communication Magazine. 1997, no. 9, p. 128 - 135.
- GEJJI, R. R. Forward-link power control in CDMA cellular systems. IEEE Transactions on Vehicular Technology. 1992, vol. 41, no. 11, p. 532 - 536.
- FOO, Y. C., LIM, W. L., TAFAZOLLI, R., BARCLAY, L. W. For-ward link power control for high altitude platform stations W-CDMA system. In Proceedings of the 54th Vehicular Technology Conference 2001 Fall. 2001, p. 625 - 629.
- TAHA-AHMED, B., CALVO-RAMON, M., HARO-ARIET, L. On the downlink capacity of high altitude platform W-CDMA system. In Proceedings of IST 2003. Aviero (Portugal) 2003, p. 765 - 768.