ISSN 1210-2512 (Print)

ISSN 1805-9600 (Online)

Radioengineering

Radioeng

Proceedings of Czech and Slovak Technical Universities

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April 2003, Volume 12, Number 1

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V. Navratil, M. Leone [references] [full-text] [Download Citations]
The Effect of Differential Driver Asymmetries on Common-Mode Frequency Spectrum

A frequency spectra determination of the common-mode signal due to the differential driver asymmetries is presented. The analytical expression for the Fourier series is developed and the evaluations for different dependencies are introduced. The effect of the skew time and amplitude imbalance is shown in a parameter study. From the general analytical solution a compact expression for small amplitude imbalances is deduced. This allows to study the influence of the driver time skew on the resulting common-mode signal, which is the source of unwanted electromagnetic radiation. It is found that for realistic driver parameters, the driver skew is the most responsible.

M. Grabner, V. Kvicera [references] [full-text] [Download Citations]
Refractive Index Measurement at TV Tower Prague

Propagation related parameters are used for design and frequency planning of microwave networks. Atmospheric refractive index is the important parameter that influences the propagation of electromagnetic waves during so-called "clear sky" conditions. The refractive index measurement, which was launched in TESTCOM, is presented in this paper. Some statistical characteristics and their utilization are introduced.

O. Fiser [references] [full-text] [Download Citations]
Site Diversity Gain Estimated from Rain Rate Records

The site diversity is used to mitigate the rain attenuation on satellite links. The attenuation is estimated through the rain rate-rain attenuation conversion based on the Assis-Einloft physical model in this study. Through the comparison of instantaneous attenuations at two receiving sites the site diversity gain is estimated. Examples of rain rate measurements in the Czech Republic followed by the site diversity gain estimation are added. This gain is greater on west-east situation of receiving sites achieving 10 dB on 0.01% exceedance level/100 km.

V. Schejbal, J. Novak, S. Gregora [references] [full-text] [Download Citations]
Comparison of CAD for Rectangular Microstrip Antennas

Calculations of several cases for rectangular microstrip antennas using more accurate cavity model have been compared with the conventional cavity calculations, expressions generated by curve fitting to full wave solutions and published experimental values for a variety of different substrate thickness and patch sizes with width to length ratio of 1.5 and with r = 10.8 and r = 2.33.

V. Schejbal, Z. Raida, Z. Novacek [references] [full-text] [Download Citations]
Comparison of CAD Formulas, Method of Moments and Experiments for Rectangular Microstrip Antennas

Calculations of several cases for rectangular microstrip patch antennas using more accurate cavity model have been compared with the conventional cavity calculations, expressions generated by curve fitting to full wave solutions and method of moments. Calculated as well as experimental values have been studied for different thickness, patch sizes and substrate materials with different permittivities and losses.

P. Hajach, R. Hartansky [references] [full-text] [Download Citations]
Resistively Loaded Dipole Characteristics

Resistively loaded dipole is very often used to measuring the electromagnetic field in EMC testing. The dipole is a traveling wave antenna, where its resonance is eliminated. The paper includes the computation of the current distribution and radiation pattern of this dipole. The characteristics were obtained by moment method, Hallen method and Wu-King method. The unique modification of presented methods has been made. The comparison of used methods has been presented in paper conclusions.

T. Fryza, S. Hanus [references] [full-text] [Download Citations]
Algorithms for Fast Computing of the 3D-DCT Transform

The algorithm for video compression based on the Three-Dimensional Discrete Cosine Transform (3D-DCT) is presented. The original algorithm of the 3D-DCT has high time complexity. We propose several enhancements to the original algorithm and make the calculation of the DCT algorithm feasible for future real-time video compression.

J. Pospisil, Z. Kolka, S. Hanus, V. Michalek, J. Brzobohaty [references] [full-text] [Download Citations]
Optimized State Model of Piecewise-Linear Dynamical Systems

The conditions for an optimized design of the second dynamical system having low eigenvalue sensitivities are directly derived. Their more general form is in accordance with the previous results obtained by using linear topological conjugacy.

J. Pospisil, Z. Kolka, S. Hanus, T. Dostal, J. Brzobohaty [references] [full-text] [Download Citations]
New Second-Order Optimized Filter Design

Starting from the piecewise-linear (PWL) autonomous dynamical system optimized from the eigenvalue sensitivities viewpoint the corresponding optimized non-autonomous linear (single-input single-output) system is derived. Such a design procedure gives the possibility to obtain minimum eigenvalue sensitivities with respect to the change of the individual model parameters also for non-autonomous linear systems. Two examples of the system having the complex conjugate poles and zeros, i.e. the optimized second-order band-reject and all-pass filter design, are shown.

P. Kovar [references] [full-text] [Download Citations]
Generation of the Narrow Band Digital Modulated Signals Using Quadrature Digital Upconverter

The paper deals with the modern approach to generation of digital modulated signals at intermediate frequency in digital way. The common digital modulator is based on analogue Quadrature modulator. The modern VLSI integrated circuits enable to implement this signal processing method in digital form. Analog and digital approaches are compared in this document. The measurement of narrow band D8PSK modulation signal generated by Quadrature Digital Upconverter is presented in this paper.

K. Vlcek [references] [full-text] [Download Citations]
Advanced Error-Control Coding Methods Enhance Reliability of Transmission and Storage Data Systems

Iterative coding systems are currently being proposed and accepted for many future systems as next generation wireless transmission and storage systems. The text gives an overview of the state of the art in iterative decoded FEC (Forward Error-Correction) error-control systems. Such systems can typically achieve capacity to within a fraction of a dB at unprecedented low complexities. Using a single code requires very long code words, and consequently very complex coding system. One way around the problem of achieving very low error probabilities is turbo coding (TC) application. A general model of concatenated coding system is shown - an algorithm of turbo codes is given in this paper.

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