April 2010, Volume 19, Number 1

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V. Sebesta [references] [full-text]
Estimating a Spectral Correlation Function under the Conditions of Imperfect Relation between Signal Frequencies and a Sampling Frequency

This paper is devoted to the estimation of the spectral correlation function. The examined signal is a simple DSB-SC signal. The aim of the paper is discovering events connected with nonstandard relations between signal frequency parameters and sampling frequency. They manifest by descending the spectral correlation function modulus. The events has been described analytically and verified using computer experiments. It is shown, that influence of the inaccuracy of the frequency is stronger for modulating frequency than for carrier frequency. Small inaccuracies of the frequencies have acceptable consequences.

  1. QUAN, Z., et al. Collaborative wideband sensing for cognitive radios. IEEE Signal Processing Magazine, 2008, vol. 25, no. 6, p. 60-73.
  2. LUNDEN, J., et al. Collaborative cyclostationary spectrum sensing for cognitive radio systems. IEEE Transactions on Signal Processing, 2009, vol. 57, no. 11, p. 4182-4195.
  3. TURUNEN, V., et al. Implementation of cyclostationary feature detector for cognitive radios. In Conference on Cognitive Radio Oriented Wireless Networks and Communications, June 2009. p. 1 – 4.
  4. GARDNER, W. A. Spectral correlation of modulated signals: Part I – Analog modulation. IEEE Transactions on Communica- tions, 1987, vol. 35, no. 6, p. 584-594.
  5. ENSERINK, S., COCHRAN, D. A cyclostationary feature detector. In Proc. 28th Asilomar Conf. Signals, Systems, and Computers. Pacific Grove (CA), Nov. 1994, vol. 2, p. 806–810.
  6. GARDNER, W. A. Spectral correlation of modulated signals: Part II – Digital modulation. IEEE Transactions on Communica- tions, 1987, vol. 35, no. 6, p. 595-601.
  7. CHEN, H.-S., GAO, W., DAUT, D. G. Spectrum sensing using cyclostationarity properties and application to IEEE 802.22 WRAN. In GLOBECOM’07, 2007, p. 3133 – 3138.
  8. MITRA, S. K. Digital Signal Processing. A Computer-Based Approach. The McGraw-Hill Companies, Inc., 1998.
  9. GARDNER, W. A. Cyclostationarity in Communications and Signal Processing. IEEE PRESS, 1994.

Keywords: Spectral correlation function, feature detector, cyclic frequency, spectral frequency, frequency offset.

P. Kejík, S. Hanus [references] [full-text]
Comparison of Fuzzy Logic and Genetic Algorithm Based Admission Control Strategies for UMTS System

CDMA systems have so-called soft capacity, so the total number of possible sessions has not an exact value. The capacity of CDMA system depends on the interference level in the system. There are therefore RRM (Radio Resources Management) functions, which are responsible for supplying optimum coverage, ensuring efficient use of physical resources and providing the maximum planned capacity. This paper presents and compares several algorithms that are used for admission control purposes in UMTS system. Several versions of fuzzy logic based algorithms, load factor based algorithm and genetic based algorithm are mutually compared via simulations.

  1. ROMERO, J., SALLENT, O., AGUSTÍ, R., DÍAZ-GUERRA, M. Radio Resources Management Strategies in UMTS. Wiley & Sons, 2005. 345 pages. ISBN 978-0-470-02277-1.
  2. ELAYOUBI, S., CHAHED, T. Admission control in the downlink of WCDMA/UMTS. In Wireless Systems and Mobility in Next Generation Internet. Springer, Heidelberg, Lecture Notes in Computer Science, vol. 3427/2005, p. 136-151. ISBN 978-3-540- 25329-7.
  3. AGUSTI, R., SALLENT, O., PEREZ, J., GORIA, P., MANGANI, N., VAILLANT, A. First Report on the Evaluation of RRM Algorithms by Simulation. 2002, [online], [Cit 2008-11-24]. Document available on http://www.arrows-ist.upc.es/.
  4. SOUTO, N., SOARES, A., EUSÉBIO, P., CORREIA, A., SILVA, J. C. Effective radio resource management for multimedia broadcast/multicast services in UMTS networks. EURASIP Journal on Wireless Communications and Networking, vol. 2006, Article ID 70903, 12 pages, 2006. doi: 10.1155/WCN/2006/70903.
  5. MALARKKAN, S., RAVICHANDRAN, V. Performance analysis of call admission control in WCDMA systems with adaptive multi class traffic based on fuzzy logic. IJCSNS International Journal of Computer Science and Network Security. Nov. 2006, vol. 6, no. 11.
  6. YENER, A., ROSE, C. Genetic algorithms applied to cellular call admission problem: Local polices. In IEEE Transactions on Vehicular Technology. Feb. 1997, vol. 46, p. 72-79.
  7. SHEN, S., CHANG, C., HUANG, C., BI, Q. Intelligent call admission control for wideband CDMA cellular systems. IEEE Transactions on Wireless Communications. Sept. 2004, vol. 3, no. 5.
  8. KARABUDAK, D., HUNG, C., BING, B. A call admission control scheme using genetic algorithms. In Proceedings of the 2004 ACM symposium on Applied Computing. 2004. ISBN 1-58113-812-1.
  9. KEJÍK, P., HANUS, S. Fuzzy logic based call admission control in UMTS system. In CD: Proceedings of the 2009 1st International Conference on Wireless Communication, Vehicular Technology, Information Theory and Aerospace & Electronic System Technology. Aalborg (Denmark), 2009, p. 375-378. ISBN 978-1-4244-4067-2.
  10. KEJÍK, P., HANUS, S. The application of fuzzy logic for admission control in UMTS system. In Proceedings of the 19th International Conference Radioelektronika 2009. Bratislava (Slovak Republic), 2009, p 203-206. ISBN 978-1-4244-3536-4.
  11. LO, J., BRITO, A., CORREIA, L., CORREIA, A. Simulation of call admission control, load control, handover and power control algorithms for Enhanced-UMTS. SEACORN Project [online]. [Cit. 2009-2-3]. Document available on http://seacorn.ptinovacao.pt/.
  12. KHOJA, J., AL-SHALASH, M., PRABHU, V. Dynamic system simulator for the modelling of CDMA systems. In Proceedings of the International Mobility and Wireless Access Workshop. 2002, p. 50-58. ISBN 0-7695-1843-5.

Keywords: Admission control, CDMA, UMTS, fuzzy logic, genetic algorithm.

K. B. Baltzis [references] [full-text]
Closed-form Description of Microwave Signal Attenuation in Cellular Systems

The reliable and accurate description of signal attenuation characteristics is important in the simulation and performance analysis of wireless communications systems. Recent works have provided analytical expres- sions for the path loss statistics in cellular systems consid- ering distance-dependent losses and shadowing. In this paper, we extend this analysis by including small-scale fading. A closed-form expression that gives the path loss density in a cellular network is given. The impact of chan- nel parameters and cell size on signal attenuation is fur- ther investigated. Simulation results and comparisons with measured data in the literature verify the accuracy of the solution. The derived formulation is a useful tool for the modeling and analysis of cellular communications systems.

  1. WIESER, V., PSENAK, V. Performance of advanced hybrid link adaptation algorithms in mobile radio channel. Radioengineering, 2008, vol. 17, no. 3, p. 81-86.
  2. NOORI, N., KARIMZADEH-BAEE, R., ABOLGHASEMI, A. An empirical ultra wideband channel model for indoor laboratory environments. Radioengineering, 2009, vol. 18, no. 1, p. 68-74.
  3. BALTZIS, K. B. Current issues and trends in wireless channel modeling and simulation. Recent Patents on Computer Science, 2009, vol. 2, no. 3, p. 166-177.
  4. GHASSEMZADEH, S. S., JANA, R., RICE, C. W., TURIN, W., TAROKH, V. Measurement and modeling of an ultra-wide bandwidth indoor channel. IEEE Transactions on Communications, 2004, vol. 52, no. 10, p. 1786-1796.
  5. MORAITIS, N., CONSTANTINOU, P. Indoor channel measurements and characterization at 60 GHz for wireless local area network applications. IEEE Transactions on Antennas and Propagation, 2004, vol. 52, no. 12, p. 3180-3189.
  6. HOLIS, J., PECHAC, P. Elevation dependent shadowing model for mobile communications via high altitude platforms in built-up areas. IEEE Transactions on Antennas and Propagation, 2008, vol. 56, no. 4, p. 1078-1084.
  7. HAENGGI, M. A geometric interpretation of fading in wireless networks: Theory and applications. IEEE Transactions on Information Theory, 2008, vol. 54, no. 12, p. 5500-5510.
  8. CERRI, G., CINALLI, M., MICHETTI, F., RUSSO, P. Feed forward neural networks for path loss prediction in urban environment. IEEE Transactions on Antennas and Propagation, 2004, vol. 52, no. 11, p. 3137-3139.
  9. BHARUCHA, Z., HAAS, H. The distribution of path losses for uniformly distributed nodes in a circle. Research Letters in Communications, 2008, vol. 2008, article ID 376895, 4 pages. DOI: 10.1155/2008/376895.
  10. BALTZIS, K. B. Analytical and closed-form expressions for the distribution of path loss in hexagonal cellular networks. Wireless Personal Communications, submitted for publication.
  11. ALOUINI, M.-S., GOLDSMITH, A. J. Area spectral efficiency of cellular mobile radio systems. IEEE Transactions on Vehicular Technology, 1999, vol. 48, no. 4, p. 1047–1066.
  12. SIMON, M. K., ALOUINI, M.-S. Digital Communication over Fading Channels. 2nd ed. Chichester: John Wiley & Sons, Ltd, 2005.
  13. RUBIO, L., REIG, J., CARDONA, N. Evaluation of Nakagami fading behaviour based on measurements in urban scenarios. AEU - International Journal of Electronics and Communications, 2007, vol. 61, no. 2, p. 135–138. L., GREENSTEIN, L., MANDAYAM, N.,
  14. XIAO, PERIYALWAR, S. Distributed measurements for estimating and updating cellular system performance. IEEE Transactions on Communications, 2008, vol. 56, no. 6, p. 991-998.
  15. BALTZIS, K. B., SAHALOS, J. N. A low–complexity 3–D geometric model for the description of CCI in cellular systems. Electrical Engineering, 2009, vol. 91, no. 4, p. 211-219.
  16. PARSONS, J. D. The Mobile Radio Propagation Channel. Chichester: John Wiley & Sons, Ltd, 2000.
  17. KILLAT, M., HARTENSTEIN, H. An empirical model for probability of packet reception in vehicular ad hoc networks. EURASIP Journal on Wireless Communications and Networking, 2009, vol. 2009, article ID 721301, 12 pages. DOI: 10.1155/2009/721301.
  18. OMIYI, P., HAAS, H., AUER, G. Analysis of TDD cellular interference mitigation using busy-bursts. IEEE Transactions on Wireless Communications, 2007, vol. 6, no. 7, p. 2721-2731.
  19. THIELE, L., JUNGNICKEL, V. Out-of-channel statistics at 5.2 GHz. In Proceedings of the First European Conference on Antennas and Propagation (EuCAP 2006), Nice (France), 2006, p. 1-6. DOI: 10.1109/EUCAP.2006.4584756.
  20. ZHAO, X., KIVINEN, J., VAINIKAINEN, P., SKOG, K. Propagation characteristics for wideband outdoor mobile communications at 5.3 GHz. IEEE Journal on Selected Areas in Communications, 2002, vol. 20, no. 3, p. 507-514.
  21. CHAN, N. H. L., MATHIOPOULOS, P. T. Efficient video transmission over correlated Nakagami fading channels for IS-95 CDMA systems. IEEE Journal on Selected Areas in Communications, 2000, vol. 18, no. 6, p. 996-1011.
  22. RAPPAPORT, T. S. Wireless Communications: Principles and Practice. 2nd ed. Upper Saddle River: Prentice Hall PTR, 2002.

Keywords: Microwave propagation, path loss, fading, composite gamma-lognormal density, cellular communications.

S. D. Roy, S. Kundu [references] [full-text]
Performance of Data Services in Cellular CDMA in Presence of Soft Handoff and Packet Combining

Performance analysis of data services is studied in CDMA network in presence of soft handoff (HO) and packet combining. Packet combining in conjunction with soft handoff is found to enhance throughput, reduce delay and packet delay variation (PDV) significantly. A stop and wait automatic repeat request (ARQ) scheme has been assumed. Two different packet combining schemes for packet data service, one based on log likelihood ratio (LLR) and another based on equal gain combining (EGC) have been studied. A cross layer interactions between ARQ and packet combining at link layer and soft HO in physical layer has been shown.

  1. WONG, D., LIM, T. Soft handoff in CDMA mobile system. IEEE Personal Commun, Dec 1997, p. 6 –17.
  2. HAI JIANG, DAVIS, C. H. Coverage expansion and capacity improvement from soft handoff for cellular CDMA. IEEE Trans on Wireless Comm, Sept 2005, vol. 4, no, 5, p. 2163-2171.
  3. VITERBI, A., VITERBI, A. M., GILHOUSEN, ZEHAVI, Soft handoff extend CDMA cell coverage and increases the reverse link capacity. IEEE J. Select Areas in Commun, Oct, 1994, vol. 12, no. 8, p. 1281 –1287.
  4. NARAYANAN, K. R., STÜBER, G. L. A novel ARQ technique using the turbo coding principle. IEEE Commun. Letter, March 1997, vol. 41, p. 49–51.
  5. BEN LU, XIAODONG WANG, JUNSHAN ZHANG Throughput of CDMA data networks with multi user detection, ARQ and Packet combining. IEEE Transactions on Wireless Communica- tions, September 2004, vol. 3, no. 5, p. 1576-1589.
  6. CHASE, D. Code combining: A maximum-likelihood decoding approach for combining an arbitrary number of noisy packets. IEEE Trans. Commun., 1985, vol. 33, p. 385–393.
  7. HIROTAKE ISHIGAMI, MAYUMI SHIMOTSU, YASUNORI IWANAMI, EIJI OKAMOTO Adaptive Hybrid ARQ schemes with bit-LLR based packet combining through MIMO-OFDM eigen-mode channels. In Proceedings of IEEE TENCON, Nov. 2006, p. 1 - 4 .
  8. BUTT, M. M., FRICKE, J. CH., HOEHER, P. A. Reliability-based packet combining with application to interleave-division multiple access. In Turbo – Coding – 2006. Munich (Germany), April 3–7, 2006.
  9. DEEPAK AYYAGARI, ANTHONY EPHREMIDES Cellular multicode CDMA capacity for integrated (voice and data) services. IEEE J.Select. Areas.Commun., May 1999, vol. 17, no. 5, p. 928 to 938.
  10. KIM, J., HONIG, M. Resource allocation for multiple class of DS- CDMA traffic. IEEE Trans on Vehicular Technol, March 2000, vol. 49, no. 2, p. 506- 518.
  11. KIM, J.Y., STUBER, G.L. CDMA soft HO analysis in the presence of power control error and shadowing correlation. IEEE Trans on Wireless Comm, April 2002, vol. 1, no. 2, p. 245-255.
  12. DIPTA DAS (CHOUDHURI), KUNDU, S. Performance of packet data with variable processing gain and truncated ARQ in presence of soft handoff in cellular CDMA. In Proceedings of National Conference on Communication, 2008, IIT Bombay, p. 287-291.
  13. SKLAR, B. Turbo code concepts made easy, or how I learned to concatenate and reiterate. In Proceedings of IEEE MILCOM, 1997, vol. 1, p. 20-26.
  14. ROY, S. D., KUNDU, S. Performance of data services in cellular CDMA in presence of soft handoff and beamforming. In PIER 88, 2008, p. 73-89.
  15. ROY, S. D., KUNDU, S. Forward link data service with beamforming and soft handoff in cellular CDMA. Engineering Letter, vol. 17, no. 2, p. 63 -72.

Keywords: Packet Combining, LLR, ARQ.

P. Tesar [references] [full-text]
A New Method for Generating High Non-linearity S-Boxes

Substitution boxes are important parts in many block and stream ciphers. The emergence of a range of crypto-attacks has led to the development of criteria for repelling such attacks. The non-linearity criterion provides some protection against well- known attacks, such as linear cryptanalysis and differential cryptanalysis. The open problem is constructed by generating methods which will be rapid and will generate S-boxes with the highest possible non-linearity. This paper deals with a new rapid method for generating regular 8x8 S-boxes with non-linearity up to a value of 104. The new method combines the special genetic algorithm with total tree searching.

  1. MILLAN, W. How to improve the nonlinearity of bijective S- Boxes. In Australian Conference on Information Security and Privacy, 1998, p. 181 - 192.
  2. CLARK, J. A., JACOB, J. L., STEPNEY, S. The design of S- Boxes by simulated annealing. New Generation Computing Archive, September 2005, vol. 23, issue 3.
  3. MILLAN, W., BURNETT, L., CARTER, G., CLARK, A., DAWSON, E. Evolutionary heuristics for finding cryptographically strong S-Boxes. Springer-Verlag, Lecture Notes in Computer Science, 1999, vol. 1726, p. 263 – 274.
  4. MILLAN, W., CLARK, A., DAWSON, E. Boolean function design using hill climbing methods. In 4th Australian Conference on Information Security and Privacy. Ed. Bruce Schneier, Springer-Verlag, Lecture Notes in Computer Science, 1999, vol. 1587, p. 1 – 11.
  5. MILLAN, W., CLARK, A., DAWSON, E. Heuristic design of cryptographically strong balanced Boolean functions. In Advances in Cryptology EUROCRYPT´98, Springer-Verlag, Lecture Notes in Computer Science, 1998, vol. 1403, p. 489 – 499.
  6. BURNETT, L., CARTER, G., DAWSON, E., MILLAN, W. Efficient methods for generating MARS-Like S-Boxes. In 7th International Workshop on Fast Software Encryption 2000, Bruce Schneier, ed. Springer-Verlag, Lecture Notes in Computer Science, 2001, vol. 1978, p. 300 – 314.
  7. IZBENKO, Y., KOVTUN, V., KUZNETSOV, A. The Design of Boolean Functions by Modified Hill Climbing Method (datasheet). 17 pages. [Online] Cited 2008. Available at: http://eprint.iacr.org/2008/111.pdf
  8. Mac WILLIAMS, F.J., SLOANE, N.J.A. The Theory of Error Correcting Codes. Amsterdam: North-Holland Publishing Company, 1978.

Keywords: Cryptography, regular 8x8 S-box, non-linearity criterion, generation method.

J. Blumenstein, Z. Fedra [references] [full-text]
The PAPR and Simple PAPR Reduction of the 2D Spreading Based Communication Systems

This paper deals with Peak to Average Power Ra- tio (PAPR) characteristics and the theory of variable spread- ing factor orthogonal frequency and code division multiplex- ing (VSF-OFCDM) systems. Comparison and evaluation of PAPR of VSF-OFCDM systems with various 2D spreading factors (SF) are done in time and in frequency domain. The simple PAPR reduction approach based on random chip in- terleaving is also evaluated.

  1. FAZEL, K., KAISER, S. Multi-Carrier and Spread Spectrum Systems. 1st ed. Chichester (England): Wiley, 2003.
  2. MAEDA, N., KISHIYAMA, Y., ATARASHI, H., SAWAHASHI, M. Variable spreading factor-OFCDM with two dimensional spreading that priorizes time domain spreading for forward link broadband wireless access. IEICE Transactions on Communications, 2005, vol.E88-B, no. 2.
  3. HANZO, L., MUNSTER, M., CHOI, B. J., KELLER, T. OFDM and MC-CDMA for Boardband Multi-User Communications, WLANs and Broadcasting, 1st ed. Chichester (England): Wiley, 2004.
  4. HENG, K., ZENG, G., WANG, W. Performance analysis for OFDM-CDMA with joint frequency-time spreading. IEEE Transactions on Broadcasting, 2005, vol. 51, no. 1, p. 144-148.
  5. ATARASHI, H. Broadband Packet Wireless Access and Its Experiments. [Online] Cited 2008-04-16. Available at: www.ctr.kcl.ac.uk/pages/4gforum/2003/presentations/Asia/Atarashi.
  6. JOYDEEP, A. Two Dimensional Spreading for Doubly Dispersive Channels. Diploma thesis. New Jersey: The State University of New Jersey, 2005.
  7. BLUMENSTEIN, J., FEDRA, Z. The characteristics of the 2D spreading based communication systems. In Proceedings of 19th International Conference Radioelektronika 2009. Bratislava (Slovakia), 2009, p. 277-279.
  8. TELLADO J. Multicarrier Modulation with Low PAR Applications to DSL and Wireless. Norwell (USA): Kluwer Academic Publishers, 2000.
  9. FEDRA Z., MARSALEK R., SEBESTA V. Chip interleaving and its optimization for PAPR reduction in MC-CDMA. Radioengineering, 2007, vol. 16, no. 4, p. 19-23.

Keywords: VSF-OFCDM, OFDM-CDMA, 2D Spreading, PAPR.

A. Kalaycioglu, H. G. Ilk [references] [full-text]
A Robust Threshold for Iterative Channel Estimation in OFDM Systems

A novel threshold computation method for pilot symbol assisted iterative channel estimation in OFDM systems is considered. As the bits are transmitted in packets, the proposed technique is based on calculating a particular threshold for each data packet in order to select the reliable decoder output symbols to improve the channel estimation performance. Iteratively, additional pilot symbols are established according to the threshold and the channel is re-estimated with the new pilots inserted to the known channel estimation pilot set. The proposed threshold calculation method for selecting additional pilots performs better than non-iterative channel estimation, no threshold and fixed threshold techniques in poor HF channel simulations.

  1. DONG, X., LU, W-S., SOONG, A. C. K. Linear interpolation in pilot symbol assisted channel estimation for OFDM. IEEE Transactions on Wireless Communications, 2007, vol. 6, no. 5, p. 1910-1920.
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  4. SONG, S., SINGER, A. C., SUNG, K. M. Soft input channel estimation for turbo equalization. IEEE Transactions on Signal Processing, 2004, vol. 52, no. 10, p. 2885-2894.
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  6. VALENTI, M. C., WOERNER, B. D. Iterative channel estimation and decoding of pilot symbol assisted turbo codes over flat-fading channels. IEEE Journal on Selected Areas in Communications, 2001, vol. 19, no. 9, p. 1697-1705.
  7. FLANAGAN, M. F., FAGAN, A. D. Iterative channel estimation, equalization, and decoding for pilot-symbol assisted modulation over frequency selective fast fading channels. IEEE Transactions on Vehicular Technology, 2007, vol. 54, no. 4, p. 1661-1670.
  8. NEFEDOV, N., PUKKILA, M. Iterative channel estimation for GPRS. In The 11th IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, 2000, PIMRC 2000, vol. 2, p. 999-1003.
  9. LASAULCE, S., SELLAMI, N. On the impact of using unreliable data on the bootstrap channel estimation performance. In 4th IEEE Workshop on Signal Processing Advances Communications, SPAWC 2003, p. 348-352. in Wireless
  10. NIU, H., RITCEY, J. A. Iterative channel estimation and decoding of pilot symbol assisted LDPC coded QAM over flat fading channels. In Conference Record of the Thirty-Seventh Asilomar Conference on Signals, Systems and Computers, 2003, vol. 2, p. 2265-2269.
  11. AUER, G., BONNET, J. Threshold controlled iterative channel estimation for coded OFDM. In Proc. of IEEE 65th Vehicular Technology Conference, 2007, VTC2007-Spring, p. 1737-1741.
  12. OZBEK, B., LE RUYET, D., PANAZIO, C. Pilot-symbol-aided iterative channel estimation for OFDM-based systems. In 13th European Signal Processing Conference, EUSIPCO’05. Antalya (Turkey), 2005.
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Keywords: Adaptive threshold, additional pilot symbols, error correction decoder, soft outputs, HF.

J. Mihalik [references] [full-text]
Modeling of Human Head Surface by Using Triangular B-Splines

The paper deals with modeling of human head surface on the basis of quadratic triangular B-splines for the standard videocodec MPEG-4 SNHC. First, we define a triangular B-spline surface of any degree and then we present its calculation for modeling of the quadratic form. Next, we apply the quadratic triangular B-splines on modeling of the human head surface using 3D polygonal model Candide 3-1-6. For allocation of knots belonging to vertices of triangulation of the model, the limiting conditions are specified in the method of Monte-Carlo used for their generation. To achieve smoothness of the modeled human head surface, we propose an algorithm for calculating control points. Then for the proposed net of control points as well as the allocation of knots, the results of the modeled human head surface and its textured version using a texture of selected avatar are presented.

  1. JOSLIN, CH., PANDZIC, I, S., THALMANN, N. M. Trends in networked collaborative virtual environments. Computer Communications, 2003, vol. 26, no. 5, p. 430 – 437.
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  4. STRINTZIS, M., SARRIS, N. (Ed.). 3D modeling and Animation: Synthesis and Analysis Techniques for the Human Body. Hershey (USA): IRM Press, July 2004.
  5. MIHALIK, J., MICHALCIN, V. Animation of 3D model of human head. Radioengineering, 2007, vol. 16, no. 1, p. 58 – 66.
  6. MIHALIK, J., MICHALCIN, V. Texturing of surface of 3D human head model. Radioengineering, 2004, vol. 13, no. 4, p. 44 – 47.
  7. PIEGL, L., TILLER, W. Parametrization for surface fitting in reverse engineering. Computer Aided Geometric Design, 2001, vol. 33, no. 11, p 593 – 603.
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  11. GREINER, G., SEIDEL, H. P. Modeling with triangular B-splines. IEEE Computer Graphics and Applications, 1994, vol.14, p.56 – 60.
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  15. HARMAN, K., LABSIK, U., GREINER, G. Remeshing tri- angulated surfaces with optimal parametrizations. Computer Aided Geometric Design, 2001, vol. 33, no. 11, p.779 – 788.
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  17. DAHMEN, W., MICCHELLI, C. A. Multivariate splines – a new constructive approach. Surfaces in Computer Aided Geometric Design. Amsterdam: North-Holland, 1992.

Keywords: Triangular B-splines, modeling, human head surface, 3D polygonal model, control net.

J. Macica, P. Farkas, S. Krile [references] [full-text]
Other Computational Technique for Estimation of Lower Bound on Capacity of Two-Dimensional Diamond-1 Constrained Channel

Computational technique for lower bound on Two-dimensional Diamond-1 constrained channel capacity is presented in this paper. It is basically an amalgamation of Matrix Fractal Grow Method (MFGM) and a new Matrix Fractal Reduction Method both applicable to state transition matrices of the corresponding constrained channels and Rayleigh Quotient Iteration method. Also other programming tricks are presented which improve its implementation. Estimation of lower bound values on the mentioned capacity is made using it. The results are in good alignment with known exact results, which is a verification of the new method. The method could be generalized for other constraints which are restricted only on one neighbor symbol in 2D constrained channel such as for example Square-1 and Hexagonal-1.

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H. Yang, X. Sun, G. Sun, Z. Tian [references] [full-text]
Lossless Authentication Watermarking Based on Adaptive Modular Arithmetic

Reversible watermarking schemes based on modulo-256 addition may cause annoying salt-and-pepper noise. To avoid the salt-and-pepper noise, a reversible watermarking scheme using human visual perception characteristics and adaptive modular arithmetic is proposed. First, a high-bit residual image is obtained by extracting the most significant bits (MSB) of the original image, and a new spatial visual perception model is built according to the high-bit residual image features. Second, the watermark strength and the adaptive divisor of modulo operation for each pixel are determined by the visual perception model. Finally, the watermark is embedded into different least significant bits (LSB) of original image with adaptive modulo addition. The original image can be losslessly recovered if the stego-image has not been altered. Extensive experiments show that the proposed algorithm eliminates the salt-and-pepper noise effectively, and the visual quality of the stego-image with the proposed algorithm has been dramatically improved over some existing reversible watermarking algorithms. Especially, the stegoimage of this algorithm has about 9.9864 dB higher PSNR value than that of modulo-256 addition based reversible watermarking scheme.

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Keywords: Adaptive modular arithmetic, salt-and-pepper noise, lossless watermarking, visual perception.

Y. Xing, J. Tan [references] [full-text]
A Color Image Watermarking Scheme Resistant against Geometrical Attacks

The geometrical attacks are still a problem for many digital watermarking algorithms at present. In this paper, we propose a watermarking algorithm for color images resistant to geometrical distortions (rotation and scaling). The singular value decomposition is used for watermark embedding and extraction. The log-polar map- ping (LPM) and phase correlation method are used to register the position of geometrical distortion suffered by the watermarked image. Experiments with different kinds of color images and watermarks demonstrate that the watermarking algorithm is robust to common image processing attacks, especially geometrical attacks.

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M. Kallel, M. S. Bouhlel, J. Lapayre [references] [full-text]
Use of Multi-Watermarking Schema to Maintain Awareness in a Teleneurology Diagnosis Platform

Following the tremendous evolution of transferring images through the Internet, it is necessary to ensure security during this act, especially for medical images. The application of multiple watermarking tech- nique represents a solution to preserve the security of such data on the one hand, and the traceability of medical diagnoses made by doctors on the other hand. This falls under the remote collaborative work. This technique is applied in the TeNeCi (Collaborative tele-neurology) platform. The project allows practitioners to distribute the analyses of the medical images. In fact, we used the multiple watermarking technique in a wavelet field. The theory underlying this technique is to hide information in the medical image and at the same time to ensure its imperceptibility. The diagnosis made by the practitioner is the data inserted in the image. The fundamental challenge of this paper is how to hide the total diagnoses of each practitioner in the image ensuring a good quality of the image at the same time.

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Keywords: Multiple watermarking, medical images, TeNeCi project, wavelet transform, traceability.

M. Kubicek, Z. Kolka [references] [full-text]
Blind Oversampling Data Recovery with Low Hardware Complexity

The paper is focused on the optimization and implementation of fully digital feed-forward blind oversampling CDR (BO-CDR). Two new phase-decision algorithms are proposed. Their complexity is very low, enabling a very simple and fast implementation even in FPGA, which was used as a development platform as well as a target device for the BO-CDR block. The FPGA-based optimization gave the opportunity to perform on-the-fly optimization under real conditions of target link. This greatly shortened the development time as there were no errors caused by inaccurate simulation models.
Measurement results obtained on real links are included showing the jitter tolerance of the proposed algorithms to be comparable to the performance of modern PLL-based CDRs.

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P. Pocta, J. Holub, H. Vlckova, Z. Polkova [references] [full-text]
Impact of Different Active-Speech-Ratios on PESQ’s Predictions in Case of Independent and Dependent Losses (in Presence of Receiver-Side Comfort-Noise)

This paper deals with the investigation of PESQ’s behavior under independent and dependent loss conditions from an Active-Speech-Ratio perspective in presence of receiver-side comfort-noise. This reference signal characteristic is defined very broadly by ITU-T Recommendation P.862.3. That is the reason to investigate an impact of this characteristic on speech quality prediction more in-depth. We assess the variability of PESQ’s predictions with respect to Active-Speech-Ratios and loss conditions, as well as their accuracy, by comparing the predictions with subjective assessments. Our results show that an increase in amount of speech in the reference signal (expressed by the Active-Speech-Ratio characteristic) may result in an increase of the reference signal sensitivity to packet loss change. Interestingly, we have found two additional effects in this investigated case. The use of higher Active-Speech-Ratios may lead to negative shifting effect in MOS domain and also PESQ’s predictions accuracy declining. Predictions accuracy could be improved by higher packet losses.

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Keywords: Perceptual Evaluation of Speech Quality (PESQ), speech quality, intrusive measurement, Voice over Internet Protocol (VoIP), reference signal characteristic, Active-Speech-Ratio, comfort-noise.

P. Pecho, P. Hanacek, J. Nagy [references] [full-text]
Simulation and Evaluation of CTP and Secure-CTP Protocols

The paper discusses characteristics and qualities of two routing protocols – Collection Tree Protocol and its secure modification. The original protocol, as well as other protocols for wireless sensors, solves only problems of ra- dio communication and limited resources. Our design of the secure protocol tries to solve also the essential security ob- jectives. For the evaluation of properties of our protocol in large networks, a TOSSIM simulator was used. Our effort was to show the influence of the modification of the routing protocol to its behavior and quality of routing trees. We have proved that adding security into protocol design does not necessarily mean higher demands for data transfer, power consumption or worse protocol efficiency. In the paper, we manifest that security in the protocol may be achieved with low cost and may offer similar performance as the original protocol.

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  7. PECHO, P. Security of Wireless Sensor Networks. PhD thesis. Brno: Brno University of Technology, 2009 (to be published).
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Keywords: Routing protocol, wireless sensor networks, security.

M. Kovac, J. Kolouch [references] [full-text]
Analysis for Design and Transformation of Autosynchronous State Machines

The paper deals with design and transformation methodology of autosynchronous state machines. The result is the design methodology for autosynchronous state machines with one-hot and Gray encodings. On the basis of their simulation models the timing parameters are defined and conditions for the correct behavior are pointed out.
In order to simplify the design of these state machines, the transformation methodology of synchronous state machine in VHDL at RTL level to autosynchronous state machine is designed. These transformed state machines are compared in their chip area, power consumption and timing.

  1. REICHARDT, J., SCHWARZ, B. Digital Systems: Handout. 3rd edition. Hamburg: University of Applied Sciences. 2004. 150 p.
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Keywords: Autosynchronous circuit, state machine, VHDL, RTL, transformation, one-hot encoding, Gray encoding.

J. Lacik, I. E. Lager, Z. Raida [references] [full-text]
Multicriteria Optimization of Antennas in Time-Domain

An original approach to the time-domain multicriteria optimization of antennas is presented. For a given excitation pulse, the time-domain objective function takes the “time-domain impedance matching”, distortion of responses at the feeding point and in a desired radiating direction (with respect to the excitation pulse), and the radiated energy in the desired direction into account. The objective function is tested on the optimization of a bow-tie antenna using the particle swarm optimization. The proposed approach is suitable for the design of broadband antennas.

  1. WEILE, S. D., PISHARODY, G., CHEN, N., SHANKER, B., MICHIELSSEN, E. A novel scheme for the solution on the time- domain integral equations of electromagnetics. IEEE Transactions on Antennas and Propagation, 2004, vol. 52, no. 1, p. 283 – 295.
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  10. ROBINSON, J., RAMAT-SAMII, Y., Particle swarm optimization in electromagnetics. IEEE Transactions on Antennas and Propagation, 2004, vol. 52, no. 2, p. 397 – 407.
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Keywords: Multicriteria optimization, particle swarm optimization (PSO), time domain integral equation (TDIE).

G. S. Kirov, D. P. Mihaylova [references] [full-text]
Circularly Polarized Aperture Coupled Microstrip Antenna with Resonant Slots and a Screen

A broadband circularly polarized (CP) Aperture Coupled Microstrip Antenna (ACMSA) is described herein. In order to decrease the back radiation of the antenna due to resonant coupling slots (a cross-slot) in the ground plane, a three-layer structure with a screen is proposed. As a result, the back radiation of the antenna is reduced by more than 12 dB and its gain is increased by about 1.3 dB compared to the conventional two-layer ACMSA with nonresonant coupling slots. The antenna is designed to operate within the Ku-band. Keeping its simple and compact construction and high mechanical characteristics it can be used as an element of CP microstrip antenna arrays with various applications in the contemporary communication systems. A comparison with two similar CP antennas with resonant slots, a two-layer ACMSA and a three-layer ACMSA with a patch reflector is accomplished.

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Keywords: Aperture coupled microstrip antenna, back radiation reduction, circularly polarized microstrip antenna, cross-slot coupled, microstrip antenna with resonant slots.

P. Valtr, P. Pechac, V. Kvicera, M. Grabner [references] [full-text]
A Terrestrial Multiple-Receiver Radio Link Experiment at 10.7 GHz - Comparisons of Results with Parabolic Equation Calculations

This work presents the results of a terrestrial multiple-receiver radio link experiment at 10.7 GHz. Results are shown in the form of the power levels recorded at several antennas attached to a receiving mast. Comparisons of the measurement data with theoretical predictions using a parabolic equation technique show that, due to the complex propagation environment of the troposphere in terms of the refractive index of air, closer agreement between measurements and simulations can be achieved during periods of standard refractive conditions.

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Keywords: Microwave radio propagation, radio propagation meteorological factors, refraction, microwave propagation modeling.

P. Kovacs, Z. Raida [references] [full-text]
Global Evolutionary Algorithms in the Design of Electromagnetic Band Gap Structures with Suppressed Surface Waves Propagation

The paper is focused on the automated design and optimization of electromagnetic band gap structures suppressing the propagation of surface waves. For the optimization, we use different global evolutionary algorithms like the genetic algorithm with the single-point crossover (GAs) and the multi-point (GAm) one, the differential evolution (DE) and particle swarm optimization (PSO). The algorithms are mutually compared in terms of convergence velocity and accuracy. The developed technique is universal (applicable for any unit cell geometry). The method is based on the dispersion diagram calculation in CST Microwave Studio (CST MWS) and optimization in Matlab. A design example of a mushroom structure with simultaneous electromagnetic band gap properties (EBG) and the artificial magnetic conductor ones (AMC) in the required frequency band is presented.

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Keywords: Electromagnetic band gap (EBG), optimization, genetic algorithm (GA), differential evolution (DE), particle swarm optimization (PSO), CST Microwave Studio (CST MWS), Matlab.

T. Ince [references] [full-text]
FMCW Radar Performance for Atmospheric Measurements

Frequency-modulated continuous-wave radars (FMCW) have been used in the investigation of the atmosphere since the late 1960’s. FMCW radars provide tremendous sensitivity and spatial resolution compared to their pulsed counterparts and are therefore attractive for clear-air remote-sensing applications. However, these systems have some disadvantages and performance limitations that have prevented their widespread use by the atmospheric science community. In this study, system performance of atmospheric FMCW radar is analyzed and some measurement limitations for atmospheric targets are discussed. The effects of Doppler velocities and spectral widths on radar performance, radar’s near-field operation, and parallax errors for two-antenna radar systems are considered. Experimental data collected by the highresolution atmospheric FMCW radar is used to illustrate typical performance qualitatively based on morphological backscattered power information. A post-processing based on single-lag covariance differences between the Bragg and Rayleigh echo is applied to estimate clear-air component from refractive index turbulence and perform quantitative analysis of FMCW radar reflectivity from atmospheric targets.

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Keywords: Electromagnetic measurements, remote sensing, instruments and techniques.

C. Yang, J. Yang, M. Huang, J. Shi, J. Peng [references] [full-text]
Electromagnetic Cylindrical Transparent Devices with Irregular Cross Section

Electromagnetic transparent device is very important for antenna protection. In this paper, the material parameters for the cylindrical transparent devices with arbitrary cross section are developed based on the coordinate transformation. The equivalent two-dimensional (2D) transparent devices under TE plane and cylindrical wave irradiation is designed and studied by full-wave simulation, respectively. It shows that although the incident waves are distorted in the transformation region apparently, they return to the original wavefronts when passing through the device. All theoretical and numerical results validate the material parameters for the cylindrical transparent devices with arbitrary cross section we developed.

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Keywords: Transparent device, transformation optics, metamaterials, finite element method.

O. Baran, M. Kasal [references] [full-text]
Modeling of the Phase Noise in Space Communication Systems

Our work is focused on the investigation of an influence of an additive thermal noise and a multiplicative phase noise in space communication chains. The most important properties of both noise types are summarized. The main concern of this paper is on the multiplicative phase noise that is especially important in systems with the phase shift keying. The simulation procedure for modeling of a signal degraded by the multiplicative phase noise is described. One starts from the frequency domain, where noise properties are set up. Five basic phase noise types can be included. After a passing to the time domain, the final noisy signal is obtained. To prove the modeling correctness, two ways are used. Firstly, Allan variances are utilized as a time domain processing. Finally, for a comparison, the direct conversion formula from the frequency to the time domain is exploited. Created signal corrupted by the phase noise expresses the harmonic oscillator output signal. A pair of these oscillators, disturbed by different phase noise processes, is installed into a communication channel model and with its help, the simultaneous influence of both oscillators on the useful signal is examined. Results show a good coincidence with theoretical presumptions.

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Keywords: Multiplicative phase noise, additive thermal noise, frequency stability, oscillator, Allan variances.

Y. Liu, C. Tao [references] [full-text]
Feedback Compensation Algorithm for BPSK/QPSK Carrier Synchronization

This paper deals with carrier synchronization problem in coherent communication system, such as BPSK and QPSK. First, this paper surveys and analyzes currently existing carrier synchronization algorithms and relevant receiver structures. After an analysis of those methods, a novel algorithm called feedback compensation is proposed, including the receiver structures based on this new synchronization algorithm. This new algorithm can not only simplify the signal processing stage but also decouple the demodulator and carrier synchronization module. At last, FPGA implementation results are presented and discussed.

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Keywords: Carrier synchronization, feedback compensation, receiver structure, FPGA based implementation.

J. Rumanek, J. Sebesta [references] [full-text]
New Channel Coding Methods for Satellite Communication

This paper deals with the new progressive channel coding methods for short message transmission via satellite transponder using predetermined length of frame. The key benefits of this contribution are modification and implementation of a new turbo code and utilization of unique features with applications of methods for bit error rate estimation and algorithm for output message reconstruction. The mentioned methods allow an error free communication with very low Eb/N0 ratio and they have been adopted for satellite communication, however they can be applied for other systems working with very low Eb/N0 ratio.

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Keywords: Turbo code, coding, interleaving, MAP, decoding, bit error rate, bit error rate estimation, satellite communication.

L. Dordova, O. Wilfert [references] [full-text]
Calculation and Comparison of Turbulence Attenuation by Different Methods

This paper is focused on the effect of turbulence in atmospheric transmission media. A short introduction of the origin of turbulent atmosphere is given. Two classical methods for the calculation of turbulence attenuation are mentioned and briefly described in the paper – the Rytov approximation and Andrews’s method, and a new technique designed by the authors of this paper – the method of available power – is presented in short as well.
We have run simulations in Matlab to compare the results of turbulence attenuation given by the classical methods and by the new technique - the method of available power. These calculations were performed for communication wavelengths of 850 nm and 1550 nm. The distance between the optical transmitter and receiver of horizontal links was set to values ranging from 0 m to 2500 m. We have taken into account the homogenous turbulence with low (10^-16 m^-2/3), medium (10^-15 m^-2/3) and high (10^-14 m^-2/3) structure parameter of refractive index Cn2.

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  2. NABOULSI, A., SIZUN, M., DE FORNEL, F. Propagation of optical and infrared waves in the atmosphere. In The Proceedings of the XXVIIIth URSI General Assembly in New Delhi. New Delhi (India): URSI, 2005, p. 1 – 4.
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  5. DORDOVA, L.; WILFERT, O. Laser beam attenuation determined by the method of available optical power in turbulent atmosphere. Journal of Telecommunications and Information Technology, 2009, no. 2, p. 53-57.

Keywords: Free space optical links, turbulence attenuation, method of available power, the Rytov approximation.

O. Kucera [references] [full-text]
Electrical Analogy to an Atomic Force Microscope

Several applications of the atomic force microscopy (AFM), such as measurement of soft samples, manipulation with molecules, etc., require mechanical analysis of the AFM probe behavior. In this article we suggest the electrical circuit analogy to AFM cantilever tip motion. Well developed circuit theories in connection with fairly accessible software for circuit analysis make this alternative method easy to use for a wide community of AFM users.

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Keywords: Atomic Force Microscopy, electrical mechanical analogs, circuit theory.

P. Koudelka, B. Petrujova, J. Latal, F. Hanacek, P. Siska, J. Skapa, V. Vasinek [references] [full-text]
Optical Fiber Distributed Sensing System Applied in Cement Concrete Commixture Research

DTS are unique optical-fiber distributed systems for measuring of temperature or mechanical tension. These systems use non-linear properties of optical fibers. Optical fiber can therefore be used not only for telecommunication purposes, as is currently the case, but also as a sensor. Optical fiber used by the DTS system can be therefore imagine as thousands of sensors placed along the route, taking all advantages of optical fiber, such as resistance to electromagnetic radiation, safe use in flammable and explosive environments, resistance to aggressive environments, small sizes, easy installation and maintenance-free operation. The properties of DTS system mentioned above seem to be ideal for detailed mapping of the hydration heat of concrete mix in the transition to a rigid structure. Values based on measurements will be used to better understanding of the processes inside the concrete mixture (individual samples) and will serve to develop better and more durable mixture.

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Keywords: Optical-fiber distributed sensing systems, nonlinear effects, temperature-profile measurements, cement concrete commixture, hydration heat.

W. Chunhua, A. U. Keskin, L. Yang, Z. Qiujing, D. Sichun [references] [full-text]
Minimum Configuration Insensitive Multifunctional Current-Mode Biquad Using Current Conveyors and All-Grounded Passive Components

This paper proposes a new current conveyorbased high-output impedance single-input three-output current mode filter with minimum configuration. It contains two dual output second generation current conveyors, one third generation dual output current conveyor, and four grounded resistors and capacitors. The circuit simultaneously provides low-pass, band-pass, and high-pass filtering outputs, without any passive component matching conditions and restrictions on input signals. Additionally, the proposed circuit offers following advantages: Minimum active and passive element count, high output and low input impedances, suitable for cascading identical currentmode sections, all passive elements are grounded (no virtual grounding), low natural frequency and Q-factor sensitivities. The influences of non-ideal current conveyors on the proposed circuit are researched in the last.

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Keywords: Current conveyor, current-mode circuit, filter, parasitic impedance.

W. Chunhua, L. Yang, Z. Qiujing, F. Yu [references] [full-text]
Systematic Design of Fully Balanced Differential Current-Mode Multiple-Loop Feedback Filters Using CFBCCII

In this paper, a systematic design method producing balanced current-mode filters is proposed, using current controlled fully balanced second-generation current conveyor circuit (CFBCCII). In this method, many kind of all-pole multiple loop feedback (MF) current mode balanced filters can be obtained, all the produced filters have fully balance structures. Moreover, the frequency of the filters can be electronically adjustable. The produced nth-order filters are constructed by n CFBCCIIs and 2n grounded capacitors, no resistors are needed. The sensitivities of the filters and influences of CFBCCII parasitic elements on filters are analyzed.

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Keywords: Fully balanced, current mode, filter, current conveyor, multiple-loop feedback formatting.

D. Prasad, D. R. Bhaskar, A. K. Singh [references] [full-text]
New Grounded and Floating Simulated Inductance Circuits using Current Differencing Transconductance Amplifiers

Current differencing transconductance amplifier (CDTA) is receiving considerable attention as a building block for current-mode (CM) analog signal processing / signal generation. In this paper, new CDTA based lossless grounded and floating inductance simulation circuits have been proposed. The proposed grounded simulated inductance circuit employs two CDTAs and a single grounded capacitor whereas the floating simulated inductance circuit employs three CDTAs and a grounded capacitor. The circuit for grounded inductance does not require any realization conditions whereas in case of floating inductance only equality of two transconductances is needed (which can be easily maintained in practice by ensuring equal dc bias currents in the two transconductance amplifiers). Some sample results demonstrating the applications of the new simulated inductors using CMOS CDTAs have been given to confirm the workability of the new circuits.

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Keywords: CDTA, inductance simulation, filters.