June 2007, Volume 16, Number 2
The objective was to study uncertainty in antenna input impedance resulting from full one-port Vector Network Analyzer (VNA) measurements. The VNA process equation in the reflection coefficient ρ of a load, its measurement m and three errors Es, determinable from three standard loads and their measurements, was considered. Differentials were selected to represent measurement inaccuracies and load uncertainties (Differential Errors). The differential operator was applied on the process equation and the total differential error dρ for any unknown load (Device Under Test DUT) was expressed in terms of dEs and dm, without any simplification. Consequently, the differential error of input impedance Z -or any other physical quantity differentiably dependent on ρ- is expressible. Furthermore, to express precisely a comparison relation between complex differential errors, the geometric Differential Error Region and its Differential Error Intervals were defined. Practical results are presented for an indoor UHF ground-plane antenna in contrast with a common 50 Ω DC resistor inside an aluminum box. These two built, unshielded and shielded, DUTs were tested against frequency under different system configurations and measurement considerations. Intermediate results for Es and dEs characterize the measurement system itself. A number of calculations and illustrations demonstrate the application of the method.
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Keywords: Microwave measurements, network analyzer, meas-urement errors, reflection coefficient, antenna input impedance
In case of particular ultra wideband applications (i.e. radar, positioning, etc.), it is crucial to know the transient responses of antennas. In the first part of the paper, the optimization process searches for the dipole shape that accomplishes two required parameters i.e. a good matching and a minimal distortion. The particle swarm optimization method was used in the process of the dipole shape optimization. As a result, the optimized ultra wideband dipole is perfectly matched. Moreover, it minimally distorts the applied signal. The second part of the paper discusses the influence of the feeding circuit on radiating parameters and on the dipole antenna matching.
- Federal Communications Commission, First Order and Report, Revision of Part 15 of the Commission's Rules Regarding UWB Transmission Systems, FCC 02-48, April 22, 2002.
- PIKSA, P., SOKOL, V. Small Vivaldi antenna for UWB. In Proceedings of the Conference RADIOELEKTRONIKA 2005. Brno (Czech Republic), 2005, p. 490-493.
- CERNY, P., MAZANEK, M. Optimized ultra wideband dipole antenna. In Proceedings of the 18th International Conference of Applied Electromagnetics and Communications. Dubrovnik (Croatia), 2005.
- CERNY, P., MAZANEK, M., PIKSA, P., SOKOL, V., KORINEK, T. Transient response optimization of ultra wideband antennas (using particle swarm optimization). In Proceedings of the European Conference on Antennas and Propagation. Nice (France), 2006, p. 168.
- SCHANTZ, H. G. Bottom fed planar elliptical UWB antennas. In Proceedings of the Ultra Wideband Systems and Technologies. Reston (USA), 2003, p. 219-223.
- ROBINSON, J., RAHMAT-SAMII, Y. Particle swarm optimization in electromagnetics. IEEE Transactions on Antennas and Propagation, 2004, vol. 52, no. 2, p. 397-407.
- KI-HAK KIM, YOUNG-JUN CHO, SOON-HO HWANG. Design of a Band-rejected UWB planar monopole antenna with two parasitic patches. In Proceedings of the Conference ISAP2005. Seoul (Korea), 2005, p. 957-960.
Keywords: Ultra wideband antennas, UWB, particle swarm optimization, PSO, transient response radiation, dipole feeding
Ultra-weak photon emission in the visible range was measured on palm and dorsal side of left and right hand by means of a low noise photomultiplier system. To study the dynamics of this photon emission in a 24 h period photon emission was recorded in 2 h intervals in 5 experiments, utilizing strict protocols for dark adaptation and recording of subjects.
Fluctuations in photon emission in the course of 24 h period were demonstrated for each anatomic location. Mean photon emission over the 24 h period differed both between subjects and hand locations. To detect a pattern in the fluctuations the mean value for each location of each subject in each experiment was utilized to calculate fluctuations during the course of 24 h for each anatomical location.
The fluctuations in photon emission in the course of 24 h were more at dorsal sides than palm sides. The correlation between fluctuations in palm and dorsal side was not apparent. During the 24 h period a change in left-right symmetry occurred for the dorsal side but not for the palm of the hands. Photon emission at the left dorsal location was high at night, while the right dorsal side emitted most during the day.
It is concluded that a daily rhythm in photon emission can be recorded from both the dorsal and palm sides of the hands.
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Keywords: Biophoton, ultra-weak photon emission, bio-photonics, hand dorsum, palm, left-right symmetry, hand
Microwave hyperthermia appears as an adjuvant technique to heat relatively small tumors in a minimally invasive way. As this technique is based on interstitial antennas, we propose a review of the physical phenomena involved in the radiation of such antennas in a dispersive medium, using the different analytical modeling developed since the 1970\'s. These modeling have been implemented in a freely available software tool, that will allow antenna designers and medical researchers to perform rapid parameter studies to further understand the role of the several parameters involved; this tool will also help the interpretation of results issued from numerical simulations. Simulation results associated with different antenna geometries are presented and compared to results obtained by several authors.
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Keywords: Insulated antenna, dipole antennas, radiation, hyper-thermia, dissipative media, microwave antenna arrays
In this paper a new method is described for multibeam antennas synthesis where both the amplitude and phase of each radiating element is a design variable. The developed optimization method made possible to solve the synthesis problem and to answer all the constraints imposed by the radiation pattern. Two approaches for visualizing satellite antenna radiation patterns are presented. Gain-level contours drawn over a geographical map gives clearest qualitative information. A three-dimensional (3D) surface plot displays the qualitative shape of the radiation pattern more naturally. The simulations results have shown power, precision and speed of the variational method with respect to the constraints imposed on radiation pattern of the of multibeam antennas network.
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Keywords: Multibeam antennas, optimization, radiation pattern synthesis, variational method
The optimization of a switched-capacitor filter, which implements a biquadratic section, is described in this paper. The aim of the optimization is to obtain a required magnitude frequency response of the filter. The optimization takes into account both one of the features of real switches - their on-state resistance, and the features of real operational amplifiers - finite voltage gain and finite unity-gain bandwidth. An optimal dynamic range is to be achieved as well. The differential evolution - a kind of evolutionary algorithms - is employed for the optimization. The filter is designed by the usual way with ideal switches and ideal operational amplifiers at first. The analysis of this filter with real switches and real operational amplifiers proves that there is a significant difference between its magnitude frequency response and the one with ideal components. Hence, the optimization is applied for finding component values so that the magnitude frequency response is as similar to the one with ideal components as possible. As for other main real features of operational amplifiers - input and output resistance - it is shown that their effect is small.
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Keywords: Switched-capacitor circuit, band-pass filter, optimiza-tion, evolutionary algorithm, differential evolution
We propose in this paper a new simple continuous-time piecewise-linear three dimensional system for chaos generation. Nonlinearity in this model is introduced by the characteristic function of the Chua\'s circuit given in . Simulated results of some chaotic attractors are shown and justified numerically via computing the largest Lyapunov exponent. The possibility and the robustness of the circuitry realization is also given and discussed.
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Keywords: Piecewise-linear system, new chaotic attractor, circuitry realization, Chua’s diode
This paper presents the design and analysis of the OFDM modulator for Digital Radio Mondiale (DRM) standard. Attention is paid to the digital signal processing in FPGA devices. The system performs carrier modulation of the complex envelope of the DRM signal. It generates a phase modulated carrier and a magnitude signal that are used with a Pulse Step Modulation (PSM) transmitter. The system has been implemented by using VHDL language. Altera FPGA development kit with an additional board is used and functional tests and measurements are presented. Simulations evaluating the quality of the output signal were done.
- Digital Radio Mondiale (DRM); System Specification (ETSI ES 201 980 V2.1.1 2004-06), ETSI Standard, 2004.
- ETSI EN 302 245-2 V1.1.1 (2004-11): Electromagnetic compatibility and Radio spectrum Matters (ERM); Transmitting equipment for the Digital Radio Mondiale (DRM) broadcasting service; Part 2: Harmonized EN under article 3.2 of the R&TTE Directive.
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- ULOVEC, K. Measurement on DRM Transmitter. In Radioelektronika 2006 - Conference Proceedings. Bratislava (Slovak Republic), Slovak University of Technology, 2006, pp. 129-132. ISBN 80-227-2388-6.
Keywords: OFDM, FPGA, modulator, DRM, digital signal processing
This paper deals with the application of phase change materials (PCM) for thermal management of integrated circuits as a viable alternative to active forced convection cooling systems.
The paper presents an analytical description and solution of heat transfer, melting and freezing process in 1D which is applied to inorganic crystalline salts. There are also results of numerical simulation of a real 3D model. These results were obtained by means of the finite element method (FEM). Results of 3D numerical solutions were verified experimentally.
- ADAM, J. Warme- und Kuhlmanagement in elektronischen Geraten. Elektronik Praxis, 2007, vol. 3, p. 74-76.
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Keywords: Phase change, FEM, heat, integrated circuit
This contribution deals with the problem of automatic phoneme segmentation using HMMs. Automatization of speech segmentation task is important for applications, where large amount of data is needed to process, so manual segmentation is out of the question. In this paper we focus on automatic segmentation of recordings, which will be used for triphone synthesis unit database creation. For speech synthesis, the speech unit quality is a crucial aspect, so the maximal accuracy in segmentation is needed here. In this work, different kinds of HMMs with various parameters have been trained and their usefulness for automatic segmentation is discussed. At the end of this work, some segmentation accuracy tests of all models are presented.
- KROUL, M. Triphone-Based Speech Synthesis. Diploma thesis, Technical University of Liberec, 2006. (in Czech)
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Keywords: Speech processing, automatic segmentation, speech database, HMM, monophones, triphones, alignment
Nowadays, hand-held ultrasonic Doppler units are often used for noninvasive screening of atherosclerosis in arteries of the lower limbs. The mean velocity of blood flow in time and blood pressures are measured on several positions on each lower limb. This project presents software that is able to analyze such data and classify it in real time into selected diagnostic classes. It is also capable of giving a notice of some errors encountered during measuring. At the Department of Functional Diagnostics in the Regional Hospital of Liberec a database of several hundreds signals was collected. In cooperation with the specialist, the signals were manually classified into four classes. Consequently selected signal features were extracted and used for training a distance and a Bayesian classifier. Another set of signals was used for evaluating and optimizing the parameters of the classifiers. This paper compares the results of the software with those provided by a human expert. They agreed in 89 % cases.
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Keywords: Medical data recognition, hand-held ultrasonic Doppler unit, peripheral arterial disease
In this paper a scheme for utilizing shape independent basis functions for a hierarchical multiresolution image compression is shown. First, an image is segmented and its segments\' boundaries are polygon approximated, thus achieving an image mask. Second, this image mask and the image are used as an input of a three-level hierarchical encoder. The hierarchical encoder subsamples the image and the image mask and encodes them shape independently; it produces an output bit stream on a respective level that is also used on lower level(s) for further coding. On the base level a triangulation of the image mask is performed for superior performance. Another compression mode is, hence, introduced for the shape independent transform coding.
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Keywords: Image compression, hierarchical multiresolution encoding, shape independent transform
The submitted paper deals with separate scanning of individual image segments. A new image processing approach based on image segmentation and segment scanning is presented. The resulting individual segments 1-dimensional representation provides higher neighbor pixel similarity than the 1-dimensional representation of the original image. This increased adjacent pixel similarity was achieved even without application of different recursive 2-dimensional scanning methods , such as Peano-Hilbert scanning method . The resulting 1-dimensional image representation provides a good base for applying lossless compression methods, such as the entropic coding. The paper contains also results analysis of the traditional method scanned segment pixels and adjacent pixel differences from the entropy point of view. As these results indicate the lossy compression methods could be applicable using this approach as well and might improve the final results as confirmed by simple prediction algorithm results presented in this paper. More complex and sophisticated lossy compression algorithms application will be a part of the future work.
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- PAVLOVICOVA, J., ORAVEC, M., MOKOS, M., KELESI, M., Error concealment using neural networks for block-based image coding. In Proc. of the 5th EURASIP Conference focused on Speech and Image Processing, Multimedia Communications and Services. Smolenice (Slovakia), 2005, pp. 52-57.
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Keywords: Segmentation, scanning, adjacent pixel similarity, pixel differences