J. R. Mosig, M. Mazanek, M. Polivka [full-text] [Download Citations]
Guest Editorial Special Issue towards EuCAP 2012 “Emerging Materials, Methods, and Technologies in Antenna & Propagation”

M. Guardiola, L. Jofre, S. Capdevila, S. Blanch, J. Romeu [references] [full-text] [Download Citations]
3D UWB Magnitude-Combined Tomographic Imaging for Biomedical Applications. Algorithm Validation

Biomedical microwave imaging is a topic of continuous research for its potential in different areas especially in breast cancer detection. In this paper, 3D UWB Magnitude-Combined tomographic algorithm is assessed for this recurrent application, but also for a more challenging one such as brain stroke detection. With the UWB Magnitude-Combined concept, the algorithm can take advantage of both the efficiency of Fourier Diffraction Theorem-based tomographic formulation and the robustness and image quality improvement provided by a multi-frequency combination.

1. NASS, S. J., HENDERSON, I. C., LASHOF, J. C. Mammography and Beyond: Developing Technologies for the Early Detection of Breast Cancer. Washington D.C. (USA), National Academies Press, 2001.
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Keywords: Tomography, Biomedical Imaging, Microwave Imaging, Breast Cancer, Brain Stroke, Experimental Verification

J. Lizarraga, C. del-Rio [references] [full-text] [Download Citations]
Resolution Capabilities of Future THz Cameras

THz technology for developing imaging systems has recently aroused great interest, mainly due to the large number of applications in which these frequencies can be used: security, vision in hard environments, etc. In this paper we propose a method that reduces significantly the number of detectors needed for achieving certain resolution by means of diffraction that paradoxically is its main limiting factor in current imaging devices. The method uses diffraction as a way of achieving the advantages of the spatial diversity (information spread over a set of detectors) giving also the possibility to increase the resolution of the obtained images interpolating samples between detectors thanks to the slow variation function created by the diffraction phenomena.

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6. ERSOY, O. K. Diffraction, Fourier Optics and Imaging. Hoboken: Wiley, 2007.

Keywords: Terahertz cameras, Resolution, CCD

E. Perret, M. Hamdi, A. Vena, F. Garet, M. Bernier, L. Duvillaret, S. Tedjini [references] [full-text] [Download Citations]
RF and THz Identification Using a New Generation of Chipless RFID Tags

This article presents two chipless RFID approaches where data are reading using electromagnetic waves and where the medium encoding the data is completely passive. The former approach rests on the use of RF waves (more precisely the ultra-wide band UWB). The tags developed for this application are comparable with very specific, planar, conductive, radar targets where the relation between the tag geometry and its electromagnetic signature is perfectly known and is used to encode the data. The principle of operation as well as the realization process of the RF tags presented in this paper is similar to those already reported in the literature. However, contrary to the majority of chipless RFID tags, these labels do not present an antenna function dissociated from the circuit part where the data are stored. Here, functions such as the receiver, the treatment and the emitter of the signal are closely dependent. The data storage capacity of the RF chipless tags is proportional to of the used frequency bandwidth. As radio spectrum is regulated, the number of possible encoding bits is thus strongly limited with this technology. This is the reason why we introduce a new family of tags radically different from the preceding one, where data is encoded in volume thanks to a multilayer structure operating in the THz domain. These two approaches although different are complementary and allow to increase significantly the data storage capacity of the chipless tags. Simulation and experimental results are reported in this paper for both configurations. We demonstrate a coding capacity of 3.3 bit/cm2 for RFID chipless tags and a potential 10 bits coding capacity in the THz domain.

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Keywords: Chipless RFID, THz identification, Electromagnetic response, Photonic Band Gap

A. G. Dimitriou, A. Bletsas, A. C. Polycarpou, J. N. Sahalos [references] [full-text] [Download Citations]
Theoretical Findings and Measurements on Planning a UHF RFID System inside a Room

This paper investigates the problem of improving the identification performance of a UHF RFID system inside a room. We assume static reader, passive tags and availability of commodity antennas. A ray-tracing propagation model is developed that includes multipath in 3D space. It is found that careful selection of reader antenna placement and tilting must be performed to control destructive interference effects. Furthermore, 3D coverage performance gains on the order of 10% are observed by implementing tags’ diversity. A device that successfully manipulates destructive interference is introduced. All theoretical findings are verified by measurements. Finally, a method to perform propagation measurements with commodity RFID hardware is demonstrated.

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Keywords: Radio Frequency Identification, Planning, UHF, Tags, Diversity

Z. Lai, G. De La Roche, N. Bessis, P. Kuonen, G. Clapworthy, D. Zhou, J. Zhang [references] [full-text] [Download Citations]
Intelligent Ray Launching Algorithm for Indoor Scenarios

This article describes the indoor IRLA (Intelligent Ray Launching Algorithm), which originates from an efficient outdoor propagation prediction model. Implementation and validation are given in detail. An indoor office scenario is selected and simulations via the IRLA model and two other reference models have been performed. Predictions are analysed and recommendations are given. Results show that the indoor IRLA model is suitable for indoor wireless network planning and optimisation process.

1. CORRE, Y., LOSTANLEN, Y. Three-dimensional urban EM wave propagation model for radio network planning and optimization over large areas. IEEE Transactions on Vehicular Technology, 2009, vol. 58, no. 7, p. 3112 - 3123.
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Keywords: Intelligent Ray Launching Algorithm, Radiowave Propagation Prediction, Indoor Scenarios, Path Loss Models, In-Building Network Planning

A. Maltsev, R. Maslennikov, A. Lomayev, A. Sevastyanov, A. Khoryaev [references] [full-text] [Download Citations]
Statistical Channel Model for 60 GHz WLAN Systems in Conference Room Environment

In this work, a methodology of statistical channel modeling for 60 GHz WLAN systems is proposed and a channel model for the office conference room environment is developed. The proposed methodology takes into account the most important properties of the indoor 60 GHz propagation channel such as large propagation loss and necessity to use steerable directional antennas by the WLAN stations, quasi-optical propagation nature, clustering structure of the channel, and significant impact of the polarization characteristics. A general mathematical structure of the channel model that supports all the described 60 GHz propagation channel properties is suggested. Then the conference room scenario for 60 GHz WLAN systems is introduced. Development of the inter cluster, intra cluster, and polarization impact modeling parameters is considered in details first explaining the used methodology for each channel modeling aspect and then followed by its application to the conference room scenario. The raw data for the channel model development include the experimental results [1], [2] and ray-tracing simulations for the conference room scenario. The proposed channel modeling methodology and the developed conference room channel model were adopted by the IEEE 802.11ad committee for 60 GHz WLAN systems standardization.

1. MALTSEV, A., MASLENNIKOV, R., SEVASTYANOV, A., KHORYAEV, A., LOMAYEV, A. Experimental investigations of 60 GHz wireless systems in office environment. IEEE J. Selected Areas in Communications, 2009, vol. 27, no. 8, p.1488-1499.
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7. JACOB, M., et al. Modeling the dynamical human blockage for 60 GHz WLAN channel models. IEEE Document 802.11-10/0090r0, January 2010. Available at: https://mentor.ieee.org/802.11/ documents?is_dcn=90&is_group=00ad.
8. JACOB, M. et al. A Ray tracing based stochastic human blockage model for the IEEE 802.11ad 60 GHz channel model. In Proceedings of European Conference on Antennas and Propagation, 2011, 5p.
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10. MALTSEV, A., et al. Polarization model for 60 GHz. IEEE Document. 802.11-09/0431r0, April 2009.Available at: https://mentor.ieee.org/802.11/documents?is_dcn=431&is_group= 00ad.
11. MALTSEV, A., et al. Verification of polarization impact model by experimental data. IEEE Document 802.11-09/1011r0, September 2009. Available at: https://mentor.ieee.org/802.11/documents? is_dcn=1011&is_group=00ad.
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14. SAWADA, H., et al. Intra-cluster response model and parameter for channel modelling at 60 GHz (Part 3). IEEE Document 802.11- 10/0112r3, January 2010. Available at: https://mentor.ieee.org/ 802.11/documents?is_dcn=112&is_group=00ad.

Keywords: Statistical channel model, 60 GHz WLAN, IEEE 802.11ad

M. Kumngern [references] [full-text] [Download Citations]
New chopper modulators using differential voltage current conveyor

This paper presents new chopper modulators which can enable to assign three modulators in one circuit. Full amplitude modulators as Cowan and Ring modulators are kinds of the amplitude modulators as well. The proposed circuit is implemented from the differential voltage current conveyor, four-MOS transistors switch and two-MOS transistors inverter. The advantage of this proposed circuit is high input and low output impedance and is able to be connected with any load without buffer and the number of transistors is quite less which is suitable for integrated circuits. The technique is to control the switch by using the square pulse which is obtained from a direct signal generator. All simulation results are based on the PSPICE program simulator which confirms the performance of the proposed circuit and technique.

1. SMITH, K., SEDRA, A. The current-conveyor - a new circuit building block. IEEE Proceeding, 1968, vol. 56, p. 1368–1369.
2. SEDRA, A., SMITH, K. A second-generation current-conveyor and its applications. IEEE Transactions on Circuit Theory, 1970, vol. CT-17, p. 132–134.
3. FABRE, A., SAAID, O., WIEST, F., BOUCHERON, C. Current controlled bandpass filter based on translinear conveyors. Electronics Letters, 1995, vol. 31, p. 1727–1728.
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7. MONPAPASSORN, A. Chopper modulators using current conveyor analogue switches. Analog Integrated Circuits and Signal Processing, 2005, vol. 45, p. 155–162.
8. KUMNGERN, M., DEJHAN, K. DDCC-based quadrature oscillator with grounded capacitors and resistors. Active and Passive Electronic Components, 2009, doi: 10.115/2009/987304.

Keywords: chopper modulator, differential voltage current conveyor, Cowan modulator, ring modulator, AM modulator

J. Koton, A. Lahiri, N. Herencsar, K. Vrba [references] [full-text] [Download Citations]
Current-Mode Dual-Phase Precision Full-Wave Rectifier Using Current-Mode Two-Cell Winner-Takes-All (WTA) Circuit

In addition to the recently proposed full-wave rectifier by Prommee et al. using voltage-mode (VM)two-cell winner-takes-all (WTA) circuit, we present current-mode (CM) precision full-wave rectifier using CM two-cell WTA circuit. The popular Lazzaro’s CM WTA circuit has been employed for the purpose and there is no requirement of inverting the input signal. Also, dual complimentary phases of the output current signal are available from high-output impedance terminals for explicit utilization. As compared to many recently proposed CM rectifiers using complex active devices, e.g. dual-X current conveyor or universal voltage conveyor, our circuit is very compact and requires a total of 21 transistors. SPICE simulation results of the circuit implemented using 0.35 um TSMC CMOS technology are provided which verify the workability of the proposed circuit.

1. TIETZE, U., SCHENK, CH., GRAMM, E. Electronic Circuits- Handbook for Design and Application. Berlin: Springer, 2008.
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13. BIOLEK, D., HANCIOGLU, E., KESKIN A. U. High-performance current differencing transconductance amplifier and its application in precision current-mode rectification. AEU - International Journal of Electronics and Communications, 2008, vol. 62, no. 2, p. 92 - 96.
14. KHATEB, F., VAVRA, J., BIOLEK, D. Current-mode full-wave rectifier based on one CDTA and two diodes. Radioengineering, 2010, vol. 19, no. 3, p. 437 - 445.
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16. BOONCHU, B., SURAKAMPONTORN, W. A CMOS currentmode squarer/rectifier circuit. In Proceedings of the International Symposium on Circuits and Systems 2003. Bangkok (Thailand), 2003, p. I-405 - I-408.
17. SURACHET, K., VARAKORN, K. A high performance CMOS current-mode precision full-wave rectifier (PFWR). In Proceedings of the International Symposium on Circuits and Systems - ISCAS 2003. Bangkok (Thailand), 2003, p. I-41 - I-44.
18. KUMGERN, M., DEJHAN, K. High frequency, high precision CMOS half-wave rectifier. In Proceedings of ECTI International Conference. Chiang Rai (Thailand), 2007, vol. 1, p. 1-4.
19. KUMGERN, M., KNOBNOB, B., DEJHAN, K. High frequency and high precision CMOS half-wave rectifier. Circuits, Systems and Signal Processing, 2010, vol. 29, no. 5, p. 815 - 836.
20. KOMPAPASSORN, A., DEJHAN, K., CHEEVASUVIT, F. A fullwave rectifier using a current conveyor and current mirrors. International Journal of Electronics, 2001, vol. 88, no. 7, p. 751 - 758.
21. MINAEI, S.YUCE, E. New squarer circuits and a current-mode fullwave rectifier topology suitable for integration. Radioengineering, 2010, vol. 19, no. 4, p. 657 - 661.
22. OPRIS, I. E. Analog Rank Extractors and Sorting Networks. Ph.D. Dissertation. Stanford (UK): Stanford University, 1996.
23. MADRENAS, J., FERNANDEZ, D., COSP, J., ALVARADO, L. M., ALARCON, E., VIDAL, E., VILLAR, G. Self-controlled 4- transistor low-power min–max current selector. AEU - International Journal of Electronics and Communications, 2009, vol. 63, no. 4, p. 871 - 876.
24. DESAI, D. R., CARLETTA, J., VEILLETTE, R., HASSAN, F. Design of an accurate min-max current selector. In IEEE 53rd International Midwest Symposium on Circuits and Systems (MWCAS). Seattle (WA, USA), 2010, p. 562 - 565.
25. PROMMEE, P., CHATTRAKUN, K. Voltage-mode CMOS WTA maximum circuits and its applications. Microelectronics Journal, 2011, vol. 42, no. 1, p. 52 - 62.
26. LAZZARO, J., LYCKENBUSH, S., MALHOWAD, M. A., MEAD, C. Winner-take-all of o(n) complexity. Advances in Neural Signal Processing Systems. San Francisco (CA, USA): Morgan Kaufmann, 1989, p. 703-711.
27. SEDRA, A. SMITH, K. C. A second-generation current conveyor and its application. IEEE Transactions on Circuit Theory, 1970, vol. 17, p. 132 - 134.
28. KOTON, J., USHAKOV, P. A., VRBA, K. Voltage-mode multifunction frequency filter using DDCCs with mutually independent Q and w0 control feature. In Proceedings International Conference on Teleinformatics 2011, Brno (Czech Republic), 2011, p. 183-187.
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Keywords: Analog signal processing, current-mode, precision full-wave rectifier, instrumentation, measurement, WTA circuit.

B. Metin, N. Herencsar, K. Pal [references] [full-text] [Download Citations]
Supplementary First-Order All-Pass Filters with Two Grounded Passive Elements Using FDCCII

In this study, two novel first-order all-pass filters are proposed using only one grounded resistor and one grounded capacitor along with a fully differential current conveyor (FDCCII). There is no element-matching restriction. The presented all-pass filter circuits can be made electronically tunable due to the electronic resistors. Furthermore, the presented circuits enjoy high-input impedance for easy cascadability. The theoretical results are verified with SPICE simulations.

1. BIOLEK, D., SENANI, R., BIOLKOVA, V., KOLKA, Z. Active elements for analog signal processing: classification, review, and new proposals. Radioengineering, 2008, vol. 17, no. 4, p. 15 - 32.
2. KHAN, A., MAHESHWARI, S. Simple first order all-pass section using a single CCII. International Journal of Electronics, 2000, vol. 87, no. 3, p. 303 - 306.
3. CAM, U., CICEKOGLU, O., GULSOY, M., KUNTMAN, H. New voltage and current mode first-order all-pass filters using single FTFN. Frequenz, 2000, vol. 54, no. 7-8, p. 177 - 179.
4. TOKER, A., OZCAN, S., KUNTMAN, H., CICEKOGLU, O. Supplementary all-pass sections with reduced number of passive elements using a single current conveyor. International Journal of Electronics, 2001, vol. 88, no. 9, p. 969 - 976.
5. PANDEY, N., PAUL, S. K. All-pass filters based on CCII- and CCCII-. International Journal of Electronics, 2004, vol. 91, no. 8, p. 485 - 489.
6. METIN, B., CICEKOGLU, O. Component reduced all-pass filter with a grounded capacitor and high impedance input. International Journal of Electronics, 2009, vol. 96, no. 5, p. 445 - 455.
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9. METIN, B., PAL, K. Cascadable allpass filter with a single DO-CCII and a grounded capacitor. Analog Integrated Circuits and Signal Processing, 2009, vol. 61, no. 3, p. 259 - 263.
10. HERENCSAR, N., KOTON, J., JERABEK, J., VRBA, K., CICEKOGLU, O. Voltage-mode all-pass filters using universal voltage conveyor and MOSFET-based electronic resistors. Radioengineering, 2011, vol. 20, no. 1, p. 10 - 18.
11. KESKIN, A. U., AYDIN, C., HANCIOLU, E., ACAR, C. Quadrature oscillator using current differencing buffered amplifiers (CDBA). Frequenz, 2006, vol. 60, no. 3-4, p. 21 - 23.
12. KUMAR, P., KESKIN, A. U., PAL, K. Wide-band resistorless allpass sections with single element tuning. International Journal of Electronics, 2007, vol. 94, no. 6, p. 597 - 604.
13. KESKIN, A. U., PAL, K., HANCIOGLU, E. Resistorless first order all-pass filter with electronic tuning. International Journal of Electronics and Communications (AEU), 2008, vol. 62, no. 4, p. 304 - 306.
14. HORNG, J. W. Current conveyors based allpass filters and quadrature oscillators employing grounded capacitors and resistors. Computers and Electrical Engineering, 2005, vol. 31, no. 1, p. 81 - 92.
15. MAHESHWARI, S. High input impedance VM-APSs with grounded passive elements. IET Circuits Devices & Systems, 2007, vol. 1, no. 1, p. 72 - 78.
16. MAHESHWARI, S. High input impedance voltage-mode first-order all-pass sections. International Journal of Circuit Theory and Applications, 2008, vol. 36, no. 4, p. 511 - 512.
17. YUCE, E., MINAEI, S. Novel voltage-mode all-pass filter based on using DVCCs. Circuits, Systems and Signal Processing, 2010, vol. 29, no. 3, p. 391 - 402.
18. BIOLEK, D., BIOLKOVA, V. First-order voltage-mode all-pass filter employing one active element and one grounded capacitor. Analog Integrated Circuits and Signal Processing, 2010, vol. 65, no. 1, p. 123 - 129.
19. MAHESHWARI, S., MOHAN, J., CHAUHAN, D. S. Voltage-mode cascadable all-pass sections with two grounded passive components and one active element. IET Circuits Devices&Systems, 2010, vol. 4, no. 2, p. 113 - 122.
20. WANG, Z. 2-MOSFET transistors with extremely low distortion for output reaching supply voltage. Electronics Letters, 1990, vol. 26, no. 13, p. 951 - 952.
21. CHIU, W., LIU, S. I., TSAO, H. W., CHEN, J. J. CMOS differential difference current conveyors and their applications. IEE Proceedings - Circuits, Devices and Systems, 1996, vol. 143, no. 2, p. 91 - 96.
22. ELWAN, H. O., SOLIMAN, A. M. Novel CMOS differential voltage current conveyor and its applications. IEE Proceedings - Circuits, Devices and Systems, 1997, vol. 144, no. 3, p. 195 - 200.
23. EL-ADAWAY, A. A., SOLIMAN, A. M., ELWAN, H. O. A novel fully differential current conveyor and applications for analog VLSI. IEEE Transactions on Circuits and Systems Part II, 2000, vol. 47, no. 4, p. 306 - 313.
24. COMER, D. J., MCDERMID, J. E. Inductorless bandpass characteristics using all-pass networks. IEEE Transactions on Circuits Theory, 1968, vol. 15, no. 4, p. 501 - 503.
25. TARMY, R., GHAUSI, M. S. Very high-Q insensitive active RC networks. IEEE Transactions on Circuits Theory, 1970, vol. 17, no. 3, p. 358 - 366.
26. MOSCHYTZ, G. S. High-Q factor insensitive active RC network, similar to the Tarmy-Ghausi circuit but using single-ended operational amplifiers. Electronic Letters, 1972, vol. 8, no. 18, p. 458 - 459.
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Keywords: Analog filter, all-pass filter, cascadable filter, high-Q band-pass filter, grounded capacitor, FDCCII, MOSFET based resistors

J. Petrzela, Z.Hrubos, T. Gotthans [references] [full-text] [Download Citations]
Modeling Deterministic Chaos Using Electronic Circuits

This paper brings a note on systematic circuit synthesis methods for modeling the dynamical systems given by mathematical model. Both classical synthesis and integrator based method is demonstrated via the relatively complicated real physical systems with possible chaotic solution. A variety of the different active building blocks are utilized to make the final circuits as simple as possible while preserving easily measurable voltage-mode state variables. Brief experimental verification, i.e. oscilloscope screenshots, is presented. The observed attractors have some structural stability and good relationship to their numerically integrated counterparts.

1. LI, Z., SOH, J., WEN, CH. Switched and Impulsive Systems. Berlin: Springer, 2005.
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5. PETRZELA, J. Modeling of the Strange Behavior in the Selected Nonlinear Dynamical Systems, Part II: Analysis. Brno: Vutium Press, 2010.
6. CHEN, G., UETA, T. Chaos in Circuits and Systems. London: World Scientific, 2002.
7. PETRZELA, J., HANUS, S., KOLKA, Z. Simple chaotic oscillator: from mathematical model to practical experiment. Radioengineering, 2006, vol. 15, no. 1, p. 6 – 11.
8. SPROTT, J. C. Chaos and Time-Series Analysis. Oxford University Press, 2003.
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12. CAJKA, J., DOSTAL, T., VRBA, K. General view on current conveyors. International Journal of Circuit Theory and Applications, 2004, vol. 32, no. 3, p. 133 – 138.
13. Current Mode Multiplier EL2082 Datasheet, Elantec, 1996.
14. PETRZELA, J., SLEZAK, J. Conservative chaos generators with CCII+ based on the mathematical model of nonlinear oscillator. Radioengineering, 2008, vol. 17, no. 3, p. 19 – 24.
15. LU, J., YU, S., LEUNG, H., CHEN, G. Experimental verification of multidirectional multi-scroll chaotic attractors. IEEE Transaction on Circuit and Systems I, 2006, vol. 53, no. 1, p. 149 – 165.
16. High Speed Monolithic Operational Amplifier AD844 Datasheet, Analog Devices, 2003.
17. PETRZELA, J. Integrator-based synthesis of the selected chaotic oscillators. Slaboproudy obzor, 2009, vol. 4, no. 3, p. 9 – 12 (in Czech).
18. Low Cost Analog Multiplier AD633 Datasheet, Analog Devices, 2002.
19. SPROTT, J. C. Simple chaotic systems and circuits. American Journal Physics, 2000, vol. 68, no. 8, p. 758 – 763.
20. PETRZELA, J. Modeling of the Strange Behavior in the Selected Nonlinear Dynamical Systems, Part I: Oscillators. Brno: Vutium Press, 2008.
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Keywords: Autonomous system, state attractor, chaos, analog oscillator, dynamical motion

K. Zaplatilek, J. Leuchter [references] [full-text] [Download Citations]
Photovoltaic Panel Modeling in MATLAB® Environment

This article is focused on the original photovoltaic panel model identification method. The method is based on the measured characteristics for given irradiation. The system can automatically create a mathematical model for a particular panel, and a specific temperature. Attention is paid to the approximation error progress, which is at minimum in the Maximum Power Points (MPP). During the application of well-known Shockley’s equation to the entire panel the nonlinear and parametric power losses are corrected. This approach provides an accurate approximation with good agreement with measured data. The method can be applied to any measured photovoltaic panel. The model identification procedure and its use are demonstrated on the example of a particular panel. A detailed methodology for application is presented for users of the MATLAB environment.

1. LEUCHTER, J., BAUER, P., RERUCHA, V., BOJDA, P. Dc-Dc converters with FPGA control for photovoltaic system. In 13th Power Electronics and Motion Control Conference (EPE-PEMC 2008). Poznan (Poland), 2008, p. 422 - 427. ISBN 978-1-4244- 1741-4.
2. YUVARAJAN, S., SHOEB, J. A Fast and accurate maximum power point tracker for PV systems. In Proceedings of the 23th Applied Power Electronics Conf. and Exposition (APEC 2008). Austin (USA), 2008, p. 167 - 172. ISBN 978-1-4244-1873-2.
3. YANGJING, O., CHENGHUA, W., FENG, H. A Variable step maximum power point tracking method using Taylor mean value theorem. In Proceedings of the Power and Energy Engineering Conference (APPEEC 2010). Chengdu (China), 2010, p. 1-4. ISBN 978-1-4244-4812-8.
4. SERA, D., TEODORESCU, R., HANTSCHEL, J., KNOLL, M. Optimized maximum power point tracker for fast changing environmental conditions. In Proceedings of the IEEE International Symposium on Industrial Electronics (ISIE 2008). Cambridge (UK), 2008, p. 2401 – 2407. ISBN 978-1-4244-1665-3.
5. PATEL, H., AGARWAL, V. Maximum power point tracking scheme for PV systems operating under partially shaded conditions. IEEE Transactions on Industrial Electronics, 2008, vol. 55, no. 4, p. 1689-1698. ISSN: 0278-0046.
6. WU, L., ZHAO, Z., ZHENGMING, L., JIANZHENG, L., SHU, Y. L. Modified MPPT strategy applied in single-stage gridconnected photovoltaic system. In 9th International Conference on Electrical Machines and Systems (ICEMS 2005). Nanjing (China), 2005, p. 1027 - 1030. ISBN 7-5062-7407-8.
7. PATEL, H., AGARWAL, V. MPPT scheme for a PV-fed singlephase single-stage grid-connected inverter operating in CCM with only one current sensor. IEEE Transactions on Energy Conversion, 2009, vol. 24, no. 1, p. 256 - 263. ISSN 0885-8969.
8. FEMIA, N., PETRONE, G., SPAGNUOLO, G., VITELLI, M. Optimization of perturb and observe maximum power point tracking methods. IEEE Transactions on Industrial Electronics, 2005, vol. 20, no. 4, p. 963 - 973. ISSN 0885-8993.
9. CHIAN-SONG, Ch. T-S Fuzzy maximum power point tracking control of photovoltaic power generation systems. IEEE Transactions on Energy Conversion, 2010, vol. 25, no. 4, p. 1123 - 1132. ISSN 0885-8969.
10. LEUCHTER, J. BAUER, P. FINNEY, S. J. Modeling and experimental verification of EGS to achieve higher efficiency. In 35th Annual Conference of IEEE Industrial Electronics (IECON 2009). Porto (Portugal), 2009, p. 3983 - 3986. ISBN 978-1-4244- 4648-3.
11. PETER, P. K., AGARWAL, V. Switched capacitor dc-dc converter based maximum power point tracking of a PV source for nano satellite application. In Photovoltaic Specialists Conference (PVSC 2010). Hononulu (USA), 2010, p. 2604 - 2609. ISBN 978- 1-4244-5890-5.
12. BRUNTON, S. L., ROWLEY, C. W., KULKARNI, S. R., CLARKSON, C. Maximum power point tracking for photovoltaic optimization using extremum seeking. In Photovoltaic Specialists Conference (PVSC 2009). Philadelphia (USA), 2009, p. 13-16. ISBN 978-1-4244-2949-3.
13. MEHRNAMI, S., FARHANGI, S. A fast maximum power point tracking technique for PV powered systems. In 35th Annual Conference of IEEE Industrial Electronics (IECON 2009). Porto (Portugal), 2009, p. 42 - 46. ISBN 978-1-4244-4648-3.
14. WEIDONG, X., DUNFORD, W. G., CAPEL, A. A novel modeling method for photovoltaic cells. In 35th Power Electronics Specialists Conference (PESC 2004). Aachen (Germany), 2004, p. 1950 - 1956. ISBN 0-7803-8399-0.
15. LEUCHTER, J., RERUCHA, V., ZOBAA, A. F. Mathematical modeling of photovoltaic systems. In 14th Power Electronics and Motion Control Conference (EPE-PEMC 2010). Ohrid (Macedonia), 2010, p. 422 - 427. ISBN 978-1-4244-7856-.
16. MATHEWS, J. H., FINK, K. K. Numerical Methods Using MATLAB. Prentice-Hall Inc, 2004.
17. BANNERT, P. Mathematic Model of Photovoltaic Cell (final report). 20 pages. [Online] Cited 2011-04-12. Available at: http://www.vosvdf.cz/cmsb/userdata/487/FVS_002_cviceni/002_ mat_model_fvc.pdf (in Czech).

Keywords: Photovoltaic panel, identification, modeling, MATLAB

B. Psenicka, J. Hospodka [references] [full-text] [Download Citations]
Analysis and Synthesis of the Digital Structures by the Matrix Method

This paper presents a general matrix algorithm for analysis of digital filters. The method proposed in this paper allows not only the analysis of the digital filters, but also the construction of new structures of the canonic or non-canonic digital filter. Equivalent filters of different structures can be found according to various matrix expansions. The structures can be calculated even from transfer function or from state-space matrices and with the additional advantage of requiring minimum number of shifting elements. Traditional research methods are not able to construct the system with a minimum of the shifting operations.

1. KLEIN,W. Finite Systemtheorie. ZAMM - Jorunal of Applied Mathematics and Mechanics, 1979, vol. 59, no. 2, p. 136.
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4. SANJIT K. MITRA. Digital Signal Processing, A Computer Based Approach. New York: MCGraw-Hill, 1998, p. 212 - 213.
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6. VICH, R., SMEKAL, Z. Cıslicove Filtry. (in Czech). Prague: Ceska Matice Technicka, 2000, p. 119 - 126.
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Keywords: Digital filter design, matrix method, analysis, filter synthesis.

J. Kracek, M. Mazanek [references] [full-text] [Download Citations]
Wireless Power Transmission for Power Supply: State of Art

The wireless power supply is motivated by simple and comfortable use of many small electric appliances with low power input. This paper reviews the concepts which are suitable for wireless power transmission with respect to power supply of such appliances in small areas. The categorization of the concepts is made. The efficiency of the concepts is discussed on general base. The reference levels for exposure to electric and magnetic fields are mentioned, and maximal power delivered to an appliance by fulfillment of these levels is considered.

1. HUI, S. Y. R., HO, W. W. C. A new generation of universal contactless battery charging platform for portable consumer electronic equipment. IEEE Transactions on Power Electronics, 2005, vol. 20, no. 3, p. 620-627. Doi: 10.1109/TPEL.2005.846550.
2. SHINODA, H., MAKINO, Y., YAMAHIRA, N., ITAI, H. Surface sensor network using inductive signal transmission layer. In Proceedings of the 4th International Conf. on Networked Sensing Systems, 2007, p. 201-206. Doi: 10.1109/INSS.2007.4297420.
3. KURS, A., KARALIS, A., MOFFATT, R., JOANNOPOULOS, J. D., FISHER, P., SOLJACIC, M. Wireless power transfer via strongly coupled magnetic resonances. Science, 2007, vol. 317, p. 83-86. Doi: 10.1126/SCIENCE.1143254.
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5. ZHI WEI SIM, SHUTTLEWORTH, R., GRIEVE, B. Investigation of PCB microstrip patch receiving antenna for outdoor RF energy harvesting in wireless sensor networks. In Proceedings of the Loughborough Antennas & Propagation Conference, 2009, p. 129-132. Doi: 10.1109/LAPC.2009.5352525.
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8. STRASSNER, B., CHANG, K. 5.8 GHz circular polarized rectifying antenna for microwave power transmission. In Proc. of the 2001 IEEE MTT-S International Microwave Symp., 2001, vol. 3, p. 1859-1862. Doi: 10.1109/MWSYM.2001.967270.
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Keywords: wireless power transmission, wireless power supply

J. R. Panda, A. S. R. Saladi, R. S. Kshetrimayum [references] [full-text] [Download Citations]
A Compact Printed Monopole Antenna for Dual-band RFID and WLAN Applications

Design of a simple and compact microstrip-fed printed monopole antenna (PMA) for applications in wireless local area network (WLAN) and radio frequency identification (RFID) is presented. The dual-band operation is achieved from the 9-shaped folded antenna which is printed on a non-conductor backed dielectric. Measured percentage impedance bandwidth of the PMA at the center frequencies of 2.43 GHz and 5.24 GHz are 33.13 (2.14 GHz to 2.99 GHz) and 36.43 (4.40 GHz to 6.36 GHz) respectively. Consistent omnidirectional radiation patterns have been observed in both the frequency bands from the experimental results. The proposed antenna is simple in design and compact in size. It exhibits broadband impedance matching, consistent omnidirectional radiation patterns and appropriate gain characteristics (>2.5 dBi) in the RFID and WLAN frequency regions.

1. CHEN, H. D., CHEN, H. T. A CPW-fed dual-frequency monopole antenna. IEEE Trans. Antennas Propagat., 2004, vol. 52, no. 4, p. 978-982.
2. CHENG, C. H., LV, W. J., CHEN, Y., ZHU, H. B. A dual-band strip-sleeve monopole antenna fed by CPW. Microwave Opt. Technol. Lett., 2004, vol. 42, no.1, p. 70-73.
3. LIU, W. C., HUANG, C. C. A CPW-fed L-shaped slot planar monopole antenna for triple-band operations. Microwave Opt. Technol. Lett., 2005, vol. 44, no. 6, p. 510-512.
4. SHEN, C. A., LIN, K. H. A broadband internal planar monopole antenna for mobile phone. Microwave Opt. Technol. Lett., 2006, vol. 48, no. 4, p. 768-769.
5. SUMA, M. N., RAJ, R. K., JOSEPH, M., BYBI, P. C., MOHANAN, P. Compact dual band planar branched monopole antenna for DCS/2.4- GHz WLAN applications. IEEE Microw. Wireless Comp. Lett., 2006, vol. 16, no. 5, p. 275-277.
6. CHEN, S. Y., HSU, P. CPW-fed folded-slot antenna for 5.8 GHz RFID tags. Electron. Lett., 2004, vol. 40, no. 24, p. 1516-1517.
7. LIU, W. C., HU, P. K. Broadband CPW-fed folded-slot monopole antenna for RFID application. Electron. Lett., 2005, vol. 41, no. 17, pp. 937-939.
8. LIU, W. C., WU, C. M. CPW-fed shorted F-shaped monopole antenna for 5.8-GHz RFID applications. Microwave Opt. Technol. Lett., 2006, vol. 48, no. 3, p. 573-575.
9. LIU, W. C., KAO, P. C. Compact CPW-fed dual folded-strip monopole antenna for 5.8-GHz RFID application. Microwave Opt. Technol. Lett , 2006, vol. 48, no. 8, p. 1614-1615.
10. MA, D., ZHANG, W. X. Broadband CPW-fed RFID antenna at 5.8 GHz. Electron. Lett., 2006, vol. 42, no. 22, p. 1258-1259.
11. LIU, W. C. A coplanar waveguide-fed folded-slot monopole antenna for 5.8 GHz radio frequency identification application. Microwave Opt. Technol. Lett , 2007, vol. 49, no. 1, p. 71-74.
12. AMMANN, J. C., FARRELL, R. Dual-band monopole antenna with stagger-tuned arms for broadbanding. In IEEE International Workshop on Antenna Technology: Small Antennas and Novel Metamaterials (IWAT-2005). 2005, p. 278-281.
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Keywords: 9-shape monopole antenna, RFID, WLAN.

Ke Lu, Guang-Ming Wang, He-Xiu Xu [references] [full-text] [Download Citations]
Compact and Sharp-Rejection Bandstop Filter Using Uniplanar Double Spiral Resonant Cells

A novel compact bandstop filter composed of three cascaded uniplanar double spiral resonant cells (UDSRCs) for high attenuation rates is presented. Through the equivalent circuit prediction and parametric analysis, it is found that the UDSRC exhibits two controllable transmission zeros with great design flexibility through tuning the geometry parameters in a small range. Then, the influence of the stage separation between each UDSRC is investigated in order to get the appropriate stage separation. After optimization, a demonstration bandstop filter has been fabricated and measured. The results show that the attenuation rates on the lower and upper sides are 95dB/GHz and 155dB/GHz, respectively. Without any shunt stubs introduced, the length and width of the three cells are 28% and 4% of the guided wavelength at the mid-stopband frequency.

1. DUK-JAE, W., TAEK-KYUNG, L., JAE-WOOK, L., CHEOLSIG, P., WON-KYU, C. Novel U-slot and V-slot DGSs for bandstop filter with improved Q factor. IEEE Transactions on Microwave Theory and Techniques, June, 2006, vol. 54, no. 6, p. 2840 – 2847.
2. IAO-HUA, W., BING-ZHONG, W., HUA-LIANG, Z., KEVIN, J.C. A tunable bandstop resonator based on a compact slotted ground structure, IEEE Transactions on Microwave Theory and Techniques, September, 2007, vol. 55, no. 9, p. 1912 – 918.
3. MANDAL, M. K., MONDAL, P., Design of sharp-rejection, compact, wideband, bandstop filters. IET Microwaves, Antennas & Propagation, 2008, vol. 2, no. 4, p. 389 – 393.
4. KRISHNA VELIDI, V., BABU GUNTUPALLI, A., SUBRATA, S. Sharp-rejection ultra-wide bandstop filters. IEEE Microwave and Wireless Component Letter, 2009, vol. 19, no. 8, p. 503 – 505.
5. YUNCHUAN, G., GOUSSETIS, G., FERESIDIS, A. P., VARDAXOGLOU, J. C. Efficient modeling of novel uniplanar left-handed metamaterials. IEEE Transactions on Microwave Theory and Techniques, 2005, vol. 53, no. 4, p. 1462 – 1468.
6. KOKKINOS, T., FERESIDIS, A. P., VARDAXOGLOU, J. C. Equivalent circuit of double spiral resonators supporting backward waves. In Loughborough Antennas and Propagation Conference. Loughborough (UK), 2007, p. 289 – 292.
7. KOKKINOS, T., FERESIDIS, A. P. Low-profile folded monopoles with embedded planar metamaterial phase-shifting lines. IEEE Transactions on Antennas and Propagation, 2009, vol. 57, no. 10, p. 2997 – 3008.
8. JIA-SHENG, H., LANCASTER, M. J. Microstrip Filters for RF/Microwave Applications. New York: Wiley, 2001.

Keywords: Uniplanar double spiral resonant cells, controllable transmission zeros, compact size, high attenuation rates

K. H. Yeap, C. Y. Tham, G. Yassin, K. C. Yeong [references] [full-text] [Download Citations]
Attenuation in Rectangular Waveguides with Finite Conductivity Walls

We present a fundamental and accurate approach to compute the attenuation of electromagnetic waves propagating in rectangular waveguides with finite conductivity walls. The wavenumbers kx and ky in the x and y directions respectively, are obtained as roots of a set of transcendental equations derived by matching the tangential component of the electric field (E) and the magnetic field (H) at the surface of the waveguide walls. The electrical properties of the wall material are determined by the complex permittivity ε, permeability μ, and conductivity σ. We have examined the validity of our model by carrying out measurements on the loss arising from the fundamental TE10 mode near the cutoff frequency. We also found good agreement between our results and those obtained by others including Papadopoulos’ perturbation method across a wide range of frequencies, in particular in the vicinity of cutoff. In the presence of degenerate modes however, our method gives higher losses, which we attribute to the coupling between modes as a result of dispersion.

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21. YEAP, K. H., THAM, C. Y., YEONG, K. C., YEAP, K. H. A simple method for calculating attenuation in waveguides. Frequenz Journal of RF-Engineering and Telecommunications, 2009, vol. 63, p. 1 – 5.
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Keywords: Attenuation, rectangular waveguides, finite conductivity, electrical properties

V. Prajzler, J. Klapuch, O. Lyutakov, I. Huttel, J. Spirkova, P. Nekvindova, V. Jerabek [references] [full-text] [Download Citations]
Design, Fabrication and Properties of Rib Poly(methylmethacrylimide) Optical Waveguides

We report about design, fabrication and properties of the polymer optical waveguides deposited on silica-on-silicon substrate. The design of the waveguides is based on a concept that geometric dimensions of the single mode polymer waveguide are determined by geometrical parameters of the silica layer. The design of the waveguides was schemed for 650 nm, 850 nm, 1310 nm and 1550 nm wavelength. The design of the presented planar waveguides was realized on the bases of modified dispersion equation while the ridge waveguides design was proposed following the Fischbeck concept. Both designs were refined applying RSoft software using beam propagation method. Proposed shapes of the waveguides were etched by standard photolithography process into the silica layers and polymer waveguide layers were subsequently deposited into the treated substrate by spin coating. Poly(methylmethacrylimide) was used as the waveguide core material and polymethylmethacrylate was used as a cover protection layer. Propagation optical loss measurements were done by using the cut-back method and the best samples had optical losses lower than 0.6 dB/cm at 650 nm, 1310 nm and 1550 nm.

1. YOSHITAKE, N., TERAKAWA, Y., HOSOKAWA, H. Polymer optical waveguide devices for FTTH. In Proceedings of the Opto- Electronics and Communications Conference, 2008 and the 2008 Australian Conference on Optical Fibre Technology. Sydney (Australia), 2008, p. 1 - 2.
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6. WONG, W. H., LIU, K. K, CHAN, K. S., PUN, E. Y. B. Polymer devices for photonics applications. Journal of Crystal Growth, 2006, vol. 288, no. 1, p. 100-104.
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Keywords: Optical ridge waveguide, Polymer, Poly(methylmethacrylimide), Photolithography

V. Jerabek, I. Huttel [references] [full-text] [Download Citations]
Theoretical Model of the Bistable Semiconductor Laser Diode Based on the Rate Equations

The paper describes theoretical and experimental results that enabled the authors to proof optical bistability behavior of a specially modified bistable semiconductor laser diode (BLD) created on a structure with a saturable absorption section. A mathematical model of the light-current characteristic, condition for bistability and the basic parameters of the hysteresis loop were derived by solving a system of three rate equations. That system was used for simulation of the light-current characteristic and conditions of bistability of the realized BLDs. For selected operating points of the simulated light-current characteristic the parameters of hysteresis loop and element values of the BLD electrical equivalent circuit for small signal variations were calculated. The bistability was experimentally measured by the new time method devised for impulse bistability verification (IBV). The basic measured and calculated parameters of the hysteresis loop of the BLD light-current characteristic were compared.

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11. HILL, M. T., WAARDT, H., KHOE, G. D. All-optical flip-flop based on coupled laser diodes. IEEE J. Quantum Electronics, 2008, vol. 37, no.3, p. 405-413.

Keywords: Optical bistability, bistable semiconductor laser diode, rate equation.

H.E. Nistazakis, A.D. Tsigopoulos, M.P. Hanias, C.D. Psychogios, D. Marinos, C. Aidinis, G.S. Tombras [references] [full-text] [Download Citations]
Estimation of Outage Capacity for Free Space Optical Links Over I-K and K Turbulent Channels

The free space optical communication systems are attracting great research and commercial interest due to their capability of transferring data, over short distances, with high rate and security, low cost demands and without licensing fees. However, their performance depends strongly on the atmospheric conditions in the link’s area. In this work, we investigate the influence of the turbulence on the outage capacity of such a system for weak to strong turbulence channels modeled by the I-K and the K-distribution and we derive closed-form expressions for its estimation. Finally, using these expressions we present numerical results for various link cases with different turbulence conditions.

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31. GARCIA-ZAMBRANA, A., CASTILLO-VAZQUEZ, B., CASTILLO-VAZQUEZ, C. Average capacity of FSO links with transmit laser selection using non-uniform OOK signalling over exponential atmospheric turbulence channels. Optics Express, 2010, vol. 18, no. 19, p. 20445 - 20454.
32. NISTAZAKIS, H. E., ASSIMAKOPOULOS, V. D., TOMBRAS G. S. Performance estimation of free space optical links over negativeexponential atmospheric turbulence channels. Optik-Int. J. Light Electron Opt., 2011, doi:10.1016/j.ijleo.2011.01.013.
33. GARCIA-ZAMBRANA, A., CASTILLO-VAZQUEZ, C., CASTILLO-VAZQUEZ, B., HINIESTA-GOMEZ, A. Selection transmit diversity for FSO links over strong atmospheric turbulence channels. IEEE Photonics Technology Letters, 2009, vol. 21, no. 14, p. 1017 - 1019.
34. NISTAZAKIS, H. E., MARINOS, D., HANIAS, M., AIDINIS, C., TSILIS, M., TOMBRAS, G. S., TSIGOPOULOS, A. D., FAFALIOS, M. E. Estimation of capacity bounds of free space optical channels under strong turbulence conditions. In 18th Int. Conf. MIKON2010, 2010, Proc. in IEEE site.
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Keywords: Atmospheric turbulence, outage capacity, I-K distribution, K-distribution, free space optical channels

B. Z. Nikolic, G. T. Djordjevic, N. D. Milosevic [references] [full-text] [Download Citations]
Effects of Imperfect Reference Signal Recovery on Performance of SC and SSC Receivers over Generalized Fading Channels

This paper presents the study of the effects of imperfect reference signal recovery on the bit error rate (BER) performance of dual-branch switch-and-stay combining (SSC) and multibranch selection combining (SC) receivers in a generalized - fading channel. The average BER of binary and quaternary phase shift keying (BPSK and QPSK) is derived under the assumption that the reference carrier signal is extracted from the received modulated signal. For SSC receiver the optimal switching threshold (in a minimum BER sense) is numerically evaluated. Hereby we determine and discuss the simultaneous influence of the average signal-to-noise ratio (SNR) per bit, fading severity, product phase-locked loop (PLL) bandwidthbit duration (B_LT_b), switching threshold of SSC and diversity order of SC on BER performance. The influence of B_LT_b in different channel conditions and modulation formats is pointed out. The numerical results are confirmed by computer simulations.

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Keywords: Communication technology, phase shift keying, bit error rate, fading channel, diversity

M. R. Islam [references] [full-text] [Download Citations]
An Issue of Boundary Value for Velocity and Training Overhead Using Cooperative MIMO Technique in Wireless Sensor Network

A boundary value of velocity of data gathering node (DGN) and a critical value for training overhead beyond which the cooperative communication in wireless sensor network will not be feasible is proposed in this paper. Multiple Input Multiple Outputs (MIMO) cooperative communication is taken as an application. The performance in terms of energy efficiency and delay for a combination of two transmitting and two receiving antennas is analyzed. The results show that a set of critical value of velocity and training overhead pair is present for the long haul communication from the sensors to the data gathering node. Later a graphical relation between boundary value of training overhead and velocity is simulated. A mathematical relation between velocity and training overhead is also developed. The effects of several parameters on training overhead and velocity are analyzed.

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Keywords: Cooperative technique, data gathering node, training overhead, velocity, wireless sensor networks

R. Dolecek, J. Novak, O. Cerny [references] [full-text] [Download Citations]
Experimental Research of Harmonic Spectrum of Currents at Traction Drive with PMSM

The paper deals with the significant results of the experimental research of current harmonic spectrum of traction drive with permanent magnet synchronous motor. The experiments were done on a special workplace with a real traction drive for wheel vehicles. Current harmonic spectrum was analyzed by a specialized device on the base of central measuring station. The knowledge of current marked subharmonic components of stator winding is the most significant finding of experiments. The frequencies of these components are given by multiples of frequency of mechanical speeds. The subharmonic components also pass to input DC current of drive. This fact is important in particular from the point of view of legislative requirements to electromagnetic compatibility of drive with railway interlocking devices.

1. Standard CSN 34 2613 Railway Signalling Equipment - Track circuits and the outer conditions for their function (in Czech).
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6. VURM, J. Authorization of modern traction vehicles in Czech Republic. In Workshop on Disturbing Effects of Traction Devices and Their Elimination and Electromagnetic Compatibility. University of Pardubice, Jan Perner Transport Faculty, Pardubice 2010, ISBN 978-80-7395-255-6 (in Czech)
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11. DOLECEK, R., CERNY, O., NEMEC, Z. EMC of traction drive with permanent magnet synchronous motor. In Proc. of International Conference on Electromagnetics in Advanced Applications (ICEAA 09), Torino (Italy), September 2009.
12. QIANTAH, Z., XIAOFEI, L. Permanent magnetic synchronous motor and drives applied on a mid-size hybrid electric car. In Proc. of Vehicle Power and Propulsion Conference (VPPC'08). Harbin, September 2008, p.1-5, ISBN 978-1-4244-1848-0.
13. MUGUR, P., ROUDET, CREBIER, J. Power electronic converter EMC analysis through state variable approach techniques. IEEE Trans. Electromagnetic Compatibility, 2001, vol. 43, no. 2, p. 229- 238.
14. LETTL, J., DOLECEK, R. EMC increasing of PWM rectifier in comparison with classical rectifier. Radioengineering, 2008, vol. 17, no. 4, p. 93-100.
15. NOVAK, J. Analysis of disturbance effects of traction drives with permanent magnet synchronous motor. In Workshop on Disturbing Effects of Traction Devices and Their Elimination and Electromagnetic Compatibility. University of Pardubice, Jan Perner Transport Faculty, Pardubice 2010, ISBN 978-80-7395- 255-6 (in Czech)
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Keywords: Permanent magnet synchronous motor (PMSM), trraction drive, spectrum, harmonic component, converter, inverter, analysis

M. Hagara, P. Kulla [references] [full-text] [Download Citations]
Edge Detection with Sub-pixel Accuracy Based on Approximation of Edge with Erf Function

Edge detection is an often used procedure in digital image processing. For some practical applications is desirable to detect edges with sub-pixel accuracy. In this paper we present edge detection method for 1-D images based on approximation of real image function with Erf function. This method is verified by simulations and experiments for various numbers of samples of simulated and real images. Results of simulations and experiments are also used to compare proposed edge detection scheme with two often used moment-based edge detectors with sub-pixel precision.

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Keywords: Edge detection, sub-pixel accuracy, image processing

H. Luo, X. Sun, H. Yang, Z. Xia [references] [full-text] [Download Citations]
A Robust Image Watermarking Based on Image Restoration Using SIFT

This paper introduces a novel robust watermarking scheme for digital images, which is robust against common signal processing and geometric distortion attacks. In order to be resistant to geometric distortion attacks, the matched feature points determined by the scale-invariance feature transform (SIFT) are used for image restoration to reduce the synchronization errors caused by geometric distortion attacks. An adaptive embedding scheme is applied in discrete Fourier transform (DFT) domain of each subimage. The watermark detection decision is based on the number of matched bits between the retrieved and original watermark in the embedding image blocks. Experimental results show that the proposed watermarking is robust to common signal processing attacks and geometric distortion attacks, including rotation, scaling, cropping, shearing and some combined attacks.

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Keywords: Scale invariance feature transform, geometric attack, image restoration, image watermark.

W. Liang, X. Sun, Z. Ruan, J. Long, C. Wu [references] [full-text] [Download Citations]
A Sequential Circuit-Based IP Watermarking Algorithm for Multiple Scan Chains in Design-for-Test

In Very Large Scale Integrated Circuits (VLSI) design, the existing Design-for-Test(DFT) based watermarking techniques usually insert watermark through reordering scan cells, which causes large resource overhead, low security and coverage rate of watermark detection. A novel scheme was proposed to watermark multiple scan chains in DFT for solving the problems. The proposed scheme adopts DFT scan test model of VLSI design, and uses a Linear Feedback Shift Register (LFSR) for pseudo random test vector generation. All of the test vectors are shifted in scan input for the construction of multiple scan chains with minimum correlation. Specific registers in multiple scan chains will be changed by the watermark circuit for watermarking the design. The watermark can be effectively detected without interference with normal function of the circuit, even after the chip is packaged. The experimental results on several ISCAS benchmarks show that the proposed scheme has lower resource overhead, probability of coincidence and higher coverage rate of watermark detection by comparing with the existing methods.

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Keywords: IP reuse, VLSI, DFT, LFSR, multiple scan chains

B. Kyrbashov, I. Baronak, M. Kovacik, V. Janata [references] [full-text] [Download Citations]
Evaluation and Investigation of the Delay in VoIP Networks

The paper is focused mainly on the delay problems, which considerably influence the final quality of connections in VoIP (Voice over IP) networks. The paper provides a detailed exploration of the nature and mechanisms of the delay. The main purpose of the investigation was an attempt to formulate a mathematical model of delay in the VoIP network and its subsequent analysis by laboratory data.

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Keywords: Delay, VoIP, jitter, IxChariot

Z. Vranova, V. Ondryhal [references] [full-text] [Download Citations]
Utilization of Selected Data Mining Methods for Communication Network Analysis

The aim of the project was to analyze the behavior of military communication networks based on work with real data collected continuously since 2005. With regard to the nature and amount of the data, data mining methods were selected for the purpose of analyses and experiments. The quality of real data is often insufficient for an immediate analysis. The article presents the data cleaning operations which have been carried out with the aim to improve the input data sample to obtain reliable models. Gradually, by means of properly chosen SW, network models were developed to verify generally valid patterns of network behavior as a bulk service. Furthermore, unlike the commercially available communication networks simulators, the models designed allowed us to capture nonstandard models of network behavior under an increased load, verify the correct sizing of the network to the increased load, and thus test its reliability. Finally, based on previous experience, the models enabled us to predict emergency situations with a reasonable accuracy.

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Keywords: Communication network (CN), data mining (DM), data preparation, decision trees