# June 2002, Volume 11, Number 2

**P. Bernat, I. Balaz**
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RC Autonomous Circuits with Chaotic Behavior

The paper presents obtained results with applying the "Semi-systematic procedure for producing the chaos from quasi-sinusoidal oscillators". We applied this procedure to RC autonomous circuit and obtained two new autonomous circuits with chaotic behaviour. The two obtained circuits are presented. The usage of various non-linear devices is examined.

- BERNAT, P., BALAZ, I. A Twin-T Oscillator Modified for Chaotic Behaviour. In Proc. 2001 URSI Int. Symposium on Signals, Systems, Electronics. Tokyo (Japan), 2001, p. 323-326.
- ELWAKIL, A., KENNEDY, M., P. Chaotic Oscillator Derived from Sinusoidal Oscillator Based on the Current Feedback Op Amp. Analog Integ. Cir. Signal Proc. 2000, vol. 24, p. 239-251
- ELWAKIL, A., S., KENNEDY, M., P. A Semi-systematic Procedure for Producing Chaos from Sinusoidal Oscillator Using Diode-Inductor Composites and FET-Capacitor Composites, IEEE Transactions on CAS-I. 2000, vol. 47, no. 4., p. 582-590
- SPROTT, J., C. A new class of chaotic circuit. Physics Let-ters A. 2000, p. 19-23

**P. Galajda, D. Kocur**
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Chua's Circuit in Spread Spectrum Communication Systems

Communication system via chaotic modulations is demonstrated. It contains the well-known chaotic circuits as its basic elements - Chua's circuits. The proposed system has some standard properties of spread spectrum communication. The following advantage is found in simulations: a) Transmitted signals have broad spectra. b) Secure communications are possible in the sense that the better parameter matching is required in order to recover the signal. c) The circuit structure of the communication system is most simple and communication systems are easily built at a small outlay. Finally computer simulations are given to examine the validity of this system.

- KOCAREV L., HALLE K. S., ECKERT K., CHUA L. O., PARLITZU. Experimental demonstration of secure communicationsvia chaotic synchronization. Int. J. Bifurcation and Chaos.1992, vol. 2, no. 3, p. 709-713.
- ITOH M., MURAKAMI H. New communication systems viachaotic synchronizations and modulations. IEICE Trans. Fundamentals.1995, vol. E78-A, no. 3, p.285-290.
- SPANY V., PIVKA L. Chua's Circuit: A Paradigm for Chaos.World Scientific Series on Nonlinear Science, 1998.
- SPANY, V., PIVKA, L. Invariant manifolds and generation ofchaos. Elektrotechnicky casopis. 1988, vol. 39, p. 417-431
- GALAJDA P., GUZAN M., SPANY V. The State Space Mysterywith Negative Load in Multiple-valued Logic. Radioengineering.1999, vol. 8, no. 2, p. 2-7.
- PIVKA, L., SPANY, V. Boundary Surfaces and Basin Bifurcationsin Chua's Circuit. Journal of Circuits, Systems and Computers.1993, vol. 3, no. 2, p. 441-470.
- POSPISIL, J., KOLKA, Z., HORSKA, J., BRZOBOHATY, J.Simplest ODE Equivalents of Chua's Equations. InternationalJournal of Bifurcation and Chaos. 2000, vol. 10, no. 1, p. 1-23.
- POSPISIL, J., BRZOBOHATY, J., KOLKA, Z., HORSKA-KREUZIGEROVA, J. New Canonical State Models of Chua'sCircuit Family. Radioengineering. 1999, vol. 8, no. 3, p. 2-5.
- BERNAT, P., BALAZ, I. Chaotic Behaviour in Twin-T Oscillator.Radioelektronika 2001, p. 14-17
- GUZAN, M.: Capacity effect on multiple valued logic memory.Proceedings DSP-MCOM 2001, p. 113-116.
- CRUZ J. M. An IC Chip of Chua's Circuit. IEEE Transactionson Circuits and Systems. 1993, vol. 40, no. 10, p. 1-12.
- SPANY, V. Vyjadrenie nelinearnych charakteristik absolutnymihodnotami. (The Expression of the Non-Linear Characteristicsby Means of Absolutes Values). Slaboproudy obzor. 1988, vol.40, no. 7, p. 354-356.
- ITOH, M. Spread Spectrum Communication via Chaos. InternationalJournal of Bifurcation and Chaos. 1999, vol. 9, no. 1,p. 155-213.
- SPANY, V. Negative Load Resistance and the Basins of Attraction.Internal information on the Department of Electronicsand Multimedial Communications. 2001, p. 1-9.

**J. Pospisil, Z. Kolka, S. Hanus, J. Brzobohaty**
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Synthesis of Optimized Piecewise-Linear Systems Using Similarity
Transformation. Part III: Higher-Order Systems

State models of dynamical systems used as prototypes in their practical realization are optimized from the viewpoint of minimum eigenvalue sensitivities with respect to the change of the individual parameters. In the paper the previously published optimization design procedure for the second-order linear and piecewise-linear (PWL) autonomous dynamical systems [2] is extended also for the higher-order systems. Results obtained give the possibility to realize the third-order basic chaotic or the fourth-order hyper-chaotic oscillators.

- KOLKA, Z. Synthesis of Optimized Piecewise-Linear Systems Using Similarity transformation - Part I: Basic principles. Ra-dioengineering. 2001, vol. 10, no. 3, p. 5-7.
- POSPISIL, J., KOLKA, Z., HORSKA, J. Synthesis of Optimized Piecewise-Linear Systems Using Similarity transformation - Part II: Second-Order Systems. Radioengineering. 2001, vol. 10, no. 3, p. 8-10.
- CHUA, L. O., WU, C. W. On Linear Topological Conjugacy of Lure's Systems. IEEE Trans. CAS 43, 1996, p. 158-161.
- POSPISIL, J., BRZOBOHATY, J., KOLKA, Z., HORSKA, J. Decomposed Canonical State Models of the Third-Order Pie-cewise-Linear Dynamical Systems, Proc. ECCTD'99, Stresa, 1999, p. 181-184.
- POSPISIL, J., BRZOBOHATY, J., KOLKA, Z., HORSKA, J. Simplest ODE Equivalents of Chua's Equations. International Journal of Bifurcation and Chaos. 2000, vol. 10, no. 1, p. 1-23.
- HANUS, S. Realization of Third-Order Chaotic Systems Using Their Elementary Canonical State Models. In Proc. Radioelektronika'97, Bratislava, 1997, p. 44-45.

**J. Cajka, T. Dostal, K. Vrba**
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High-Order Lowpass Filters Using DVCC Elements

Special cells using a differential voltage current conveyor are presented. The use of these cells for high-order lowpass filter design is described. The filters can be designed to operate in different modes.

- VRBA, K., CAJKA, J. Antialiasing filters using new active elements. In Proceedings of the Euroconference Biosignal 2000. Brno, 2000, p.180 - 182
- ELWAN, H. O., SOLIMAN, A. M. Novel CMOS differential vol-tage current conveyor and its application. IEE Proceedings -Circuits Devices Syst. 1997, vol. 144, no. 3, p. 195 - 200.
- DOSTAL, T., VRBA, K., CAJKA, J. Adjoint voltage-to-current network transformation. In Proc. of the Conference RADIOELEKTRONIKA 2000. Bratislava, 2000, p. I8 - I10.
- DOSTAL, T. Modeling of modern active devices for simulation of analog circuits in PSpice. Radioengineering. 2000, vol. 9, no. 3, p. 8 - 11.

**D. Ticha, P. Martinek**
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Biquad Based on a Generalized Divider Structure

The paper deals with the biquad based on a generalized divider structure. This principle can be considered as an effective way of universal filter and equalizers synthesis, which easily realizes any general transfer function. An attention is devoted to the derivation of optimum design conditions. As shown, these conditions strongly depend on the amplifier type used. The results obtained are illustrated by some design examples.

- MARTINEK, P., BORES, P., MATZNER, I. Selective circuits containing sn immitance (in Czech). In Proceedings. of the workshop New ways in signal processing. Liptovsky Mikulas (Slovak Republic) 1990, vol. I., p. 14 - 17.
- TICHA, D., MARTINEK, P., BORES, P. Equalizers Based On A Generalized Divider Principle (in Czech). In the Proceedings. of the International Conference New ways in signal processing. Liptovsky Mikulas (Slovak Republic), 1996, vol. II., p. 8 - 11.
- VRBA, K., CAJKA, J. Special Nth-order One Ports Using Current Conveyors. In Proceedings of the International Conference CSS '96. Brno (Czech republic), 1996, vol. 2, p. 377-380.
- VRBA, K., CAJKA, J., VRBA, R. Special Transform Blocks for Higher Order Immitance Element Realization. In Proc. Int. Conf. ITHURS '96. Leon, 1996, vol. 2, p. 411-416.
- MARTINEK, P. An Optimized design of circuits containing GICs. In Proceedings of the 8th International Czech-Slovak Scientific Conference Radioelektronika '98. Brno, 1998, p. 42-45.
- TICHA, D., MARTINEK, P. Biquad Based on a Generalized Divider Structure. In Proceedings of the 1999 European Conference on Circuit Theory and Design. (ECCTD '99). Torino: Politecnico di Torino, 1999. p. 229-232.
- TICHA, D. Integrated filters for telecommunications systems (in Slovak). PhD thesis, Zilina, 2000.
- TOUMAZOU, C., LIDGEY,F.J., HAIGH,D.G. Analogue IC Design: The Current-Mode Approach. Peter Peregrinus Ltd. 1993.

**M. Kollar, V. Spany, T. Gabas**
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Autocompensative System for Measurement of the Capacitances

A simple and successful design of an autocompensative system with flip-flop sensor for measurement of capacitances is presented. The analysis of the sensor is based on the state description with the vertical rise segments of the control pulse. The theoretical results are compared with measured data and good agreement is reported.

- LIAN, W. Integrated silicon flip-flop sensor. Doctoral Thesis. Delft: Technise Universitet Delft, 1990.
- KOLLAR, M. Autocompensative system with analog feedback. Diploma Thesis. Kosice: Technical University of Kosice, 2000.
- SPANY, V., PIVKA, L. Dynamic properties of flip-flop sensors. Electrical Engineering. 1996, vol. 47, no. 7 - 8, p. 169 - 178.
- KALAKAJ, P., SPANY, V., SOLTYS, R. Flip-flop sensors with feedback. In Proceedings of the International Conference Tesla III Millenium. Belegrade (Yugoslavia), 1996, p. 145 - 149.
- LEVICKY, D., MICHAELI, L., SPANY, V., PIVKA, L., KALAKAJ, P. Autocompensative system with flip-flop sensor. In Proceedings of the International Conference. Napoli (Italy), 1996, p. 185 - 189.

**O. Gotra, W. Kalita, S. Slosarcik, A. Pietrikova, J. Saliga**
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Thermosensitive IC for Relative Temperature Determination

The functioning algorithm and the scheme of the transducer unit applied in thermosensitive IC with relative temperature reading are proposed in this paper. The principal algorithm of functioning is in the formation of current with linear dependence on absolute temperature by additional transduction of current into differential signal with value determined by relative temperature scale.

- Smart temperature sensors, Electronics & Wireless world. vol. 95, no. 1636, 1989,p.189-190.
- GOTRA Z., GOYAKA R., KALITA W., NEVMERGHYTSKA A. Energy independent micro-electronic thermometer based on liquid crystal indicator, Proceedings of 18th Conf. of ISHM Poland. Warsaw, Sept. 1994, p.129-132.
- GOTRA O., STADNYK B., GOLYAKA R., POTENCKI J.: Thermosensitive IC for relative temperature determination, Proceeding of the 22-nd Conference of IMAPS Poland, Zakopane, Oct. 1998, Krakow 1999, p.175-178.
- SIDNEY F.: Analog Integrated Circuits: Prentice-Hall, Inc., Englewood Cliffs, NJ 0732,1985, p.583.

**J. Pribil, A. Madlova**
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Two Synthesis Methods Based on Cepstral Parameterization

The paper deals with two implementations of the speech synthesis based on the cepstral representation of the human vocal tract model. Both the approaches to speech modeling are evaluated in the frequency domain. The paper also compares computational complexity of these two methods.

- VICH, R., SMEKAL, Z. LPC and CCF Vocal Tract Models in Speech Synthesis. In Proceedings of the 9th European Signal Processing Conference EUSIPCO 98, Rhodes (Greece), 1998, p.1861-1864.
- VICH, R., PRIBIL, J., PTACEK, M. Cepstrales Sprachsynthe-sesystem fur die tschechische Sprache. In 8. Konferenz Elek-tronische Sprachsignalverarbeitung, Cottbus (Germany), 1997, p. 218-225.
- VICH, R. Cepstral Speech Model, Pade Approximation, Exci-tation and Gain Matching in Cepstral Speech Synthesis. In Proceeding of the 15th Biennial International EURASIP Confe-rence Biosignal'2000, Brno, 2000, p. 77-82.
- PRIBIL, J. Pitch synchronous analysis and synthesis in cepstral speech modelling. In Proceedings of the 10th International Conference RADIOELEKTRONIKA 2000. Bratislava, 2000, p. III 13-16.
- MCAULAY, R. J., QUATIERI, T. F. Low-Rate Speech Coding Based on the Sinusoidal Model. Furui, S., Sondhi, M, M, Eds.: Advances in Speech Signal Processing, Marcel Dekker, New York, 1992.
- OPPENHEIM, A., V., SCHAFER, R., W. Discrete-Time Signal Processing. Prentice Hall, 1989.
- MADLOVA, A. Harmonic Speech Model with Cepstral Parameterization. VICH, R., ed. SPEECH PROCESSING, 10th Czech-German Workshop, Prague, 2000, p. 56-58.
- MADLOVA, A., PRIBIL, J. Comparison of two approaches to speech modelling based on cepstral description. In Proc. of the 15th Biennial International EURASIP Conference Biosignal 2000, Brno, 2000, p. 83-85.
- PRIBIL, J., MADLOVA, A. Computational complexity of two methods based on cepstral parameterization of speech signal. In Proc. of the 5th International Conference New Trends in Signal Processing, Liptovsky Mikulas (Slovakia), 2000, p. 248-251.

Keywords: Signal processing, speech processing, speech analysis and synthesis