2005/4

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    Radiation Pattern Reconstruction from the Near-Field Amplitude Measurement on Two Planes Using PSO
    (Společnost pro radioelektronické inženýrství, 2005-12) Tkadlec, Roman; Novacek, Zdenek
    The paper presents a new approach to the radiation pattern reconstruction from near-field amplitude only measurement over a two planar scanning surfaces. This new method for antenna pattern reconstruction is based on the global optimization PSO (Particle Swarm Optimization). The paper presents appropriate phaseless measurement requirements and phase retrieval algorithm together with a brief description of the particle swarm optimization method. In order to examine the methodologies developed in this paper, phaseless measurement results for two different antennas are presented and compared to results obtained by a complex measurement (amplitude and phase).
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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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    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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    New Planar and Volume Versions of a Metamaterial
    (Společnost pro radioelektronické inženýrství, 2005-12) Machac, Jan; Hudlicka, Martin; Buchar, Pavel; Zehenther, Jan
    Some characteristics of materials with negative permittivity and permeability, i.e., with a negative refrative index, known as metamaterials, are presented in this paper. Dispersion characteristics of left-handed parallel strips calculated by different methods are compared with each other. The calculated and measured dispersion and transmission characteristics of a newly proposed left-handed coplanar waveguide and of a novel volume metmaterial are shown. Simple equivalent circuits of both structures are presented together with elements values. The structures exhibit a negative refractive index in a wide frequency band.
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    Tropospheric Refraction Modeling Using Ray-Tracing and Parabolic Equation
    (Společnost pro radioelektronické inženýrství, 2005-12) Valtr, Pavel; Pechac, Pavel
    Refraction phenomena that occur in the lower atmosphere significantly influence the performance of wireless communication systems. This paper provides an overview of corresponding computational methods. Basic properties of the lower atmosphere are mentioned. Practical guidelines for radiowave propagation modeling in the lower atmosphere using ray-tracing and parabolic equation methods are given. In addition, a calculation of angle-of-arrival spectra is introduced for multipath propagation simulations.