2005/4

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    Multi-Objective Optimization of Wire Antennas: Genetic Algorithms Versus Particle Swarm Optimization
    (Společnost pro radioelektronické inženýrství, 2005-12) Lukes, Zbynek; Raida, Zbynek
    The paper is aimed to the multi-objective optimization of wire multi-band antennas. Antennas are numerically modeled using time-domain integral-equation method. That way, the designed antennas can be characterized in a wide band of frequencies within a single run of the analysis. Antennas are optimized to reach the prescribed matching, to exhibit the omni-directional constant gain and to have the satisfactory polarization purity. Results of the design are experimentally verified. The multi-objective cost function is minimized by the genetic algorithm and by the particle swarm optimization. Results of the optimization by both the multi-objective methods are in detail compared. The combination of the time domain analysis and global optimization methods for the broadband antenna design and the detailed comparison of the multi-objective particle swarm optimization with the multi-objective genetic algorithm are the original contributions of the paper.
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    Seven State PTP for Vector Network Analyzer
    (Společnost pro radioelektronické inženýrství, 2005-12) Zavodny, Vadim; Hoffmann, Karel; Skvor, Zbynek
    A new, seven-state switched perturbation two-port (PTP) for vector reflection measurement based on scalar measurement only was designed and realized in microstrip structure using PIN diodes. The structure was experimentally tested by means of vector measurements of different impedances in frequency band with relative bandwidth of 2.5 octaves. Good agreement with data obtained using a precise vector network analyzer was achieved. The new calibration method for the PTP was designed and tested on real measured data.
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    Assembly Influence on the Small-Signal Parameters of a Packaged Transistor
    (Společnost pro radioelektronické inženýrství, 2005-12) Sokol, Vratislav; Cerny, Petr; Hoffmann, Karel; Skvor, Zbynek
    A detailed analysis of the assembly influence on the small-signal parameters of a packaged transistor is presented. A new method, based on 3D field simulation and mixed-mode scattering parameters approach is proposed. Differences in scattering parameters caused by assembly change are computed using the new proposed method and compared to the standard method based on admittance matrix. The differences, accuracy, error sources and suitability of both methods are discussed. Results are verified experimentally in microstrip line for two fundamental assembly changes of a transistor in SOT 343 package in frequency range 45 MHz - 18 GHz.
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    BER and SIR Based Hybrid Link Algorithms Performance in Mobile Radio Channel
    (Společnost pro radioelektronické inženýrství, 2005-12) Wieser, Vladimir; Psenak, Vladimr
    In the next generation of mobile communication networks (B3G) the using of effective handling of radio resources is supposed (channels, power and transmission rate) with simultaneous delivery of required services, in which the quality of service (QoS) is guaranteed. In this article we have described and simulated new BER based, SIR-frame based and SIR-slot based link adaptation algorithms. Algorithms were designed to increase efficiency of data transmission among user equipment and base stations (uplink) expressed by throughput and the outage probability for each link. Simulation results of hybrid adaptation (power and modulation BPSK, QPSK, 16-QAM, 64-QAM) are compared and expressed as data throughput and outage probability for different simulation environments (pedestrian channel with mobile subscriber speed 10 km/s and vehicular channel with speed 120 km/h).
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    Shielding and Radiation Characteristics of Cylindrical Layered Bianisotropic Structures
    (Společnost pro radioelektronické inženýrství, 2005-12) Vegni, Lucio; Toscano, Alessandro
    In this paper we propose an analytical study in the spectral domain of cylindrical layered structures filled with general bianisotropic media and fed by a 3D electric source. The integrated structure is characterized in terms of transmission matrices leading to an equivalent circuit representation of the whole multilayered structure. Within the framework of this two-port formalism, we present a new contribution to the computation of the Green's function arising in the analysis of multilayered conformal integrated antennas loaded with general bianisotropic materials. We also propose an analytical study of the shielding effectiveness of general bianisotropic materials located in multilayered, cylindrical configuration. The expression of the shielded fields sustained both by plane wave and arbitrary sources is obtained in a closed analytical form. Numerical results are also presented showing effects of electromagnetic parameters on radiation pattern, matching properties and radar cross section of the integrated structure.