2006/4

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Now showing 1 - 5 of 16
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    Modeling and Optimizing Antennas for Rotational Spectroscopy Applications
    (Společnost pro radioelektronické inženýrství, 2006-12) Lukes, Zbynek; Lacik, Jaroslav; Raida, Zbynek
    In the paper, dielectric and metallic lenses are modeled and optimized in order to enhance the gain of a horn antenna in the frequency range from 60 GHz to 100 GHz. Properties of designed lenses are compared and discussed. The structures are modeled in CST Microwave Studio and optimized by Particle Swarm Optimization (PSO) in order to get required antenna parameters.
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    Multipath Propagation of UWB Through-Wall Radar and EMC Phenomena
    (Společnost pro radioelektronické inženýrství, 2006-12) Schejbal, Vladimir; Cermak, Dusan; Nemec, Zdenek; Pidanic, Jan; Konecny, Jiri; Bezousek, Pavel; Fiser, Ondrej
    The UWB (ultra wide band) radar output signals can be substantially affected due to electromagnetic wave propagation through obstacles (such as walls) and multipath effects, too. Multipath effects are analyzed and simulated numerically for various cases with several antenna heights and distances. Delays (due to propagation through walls and various paths of direct and reflected rays) and the ringing (similar to UWB propagation through wall) can be clearly observed and analyzed. Moreover, frequency spectra analyses can demonstrate both UWB interferences and susceptibility from electromagnetic compatibility (EMC) viewpoint.
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    Methods for High Power EM Pulse Measurement
    (Společnost pro radioelektronické inženýrství, 2006-12) Drexler, Petr; Fiala, Pavel
    There are some suitable methods for the measurement of ultra-short solitary electromagnetic pulses that can be generated by high power pulsed generators. The measurement methods properties have to correspond to the fact whether we want to measure pulses of voltage, current or free-space electromagnetic wave. The need for specific measurement methods occurred by the development of high power microwave pulse generator. Applicable methods are presented in this paper. The method utilizing Faraday\'s induction law allows the measurement of generated current. For the same purpose the magneto-optic method can be utilized, with its advantages. For measurement of output microwave pulse of the generator the calorimetric method was designed and realized.
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    Comparative Performance Analysis of Three Algorithms for Principal Component Analysis
    (Společnost pro radioelektronické inženýrství, 2006-12) Landqvist, Ronnie; Mohammed, Abbas
    Principal Component Analysis (PCA) is an important concept in statistical signal processing. In this paper, we evaluate an on-line algorithm for PCA, which we denote as the Exact Eigendecomposition (EE) algorithm. The algorithm is evaluated using Monte Carlo Simulations and compared with the PAST and RP algorithms. In addition, we investigate a normalization procedure of the eigenvectors for PAST and RP. The results show that EE has the best performance and that normalization improves the performance of PAST and RP algorithms, respectively.
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    A Robust Adaptive MMSE Rake Receiver for DS-CDMA System in a Fast Multipath Fading Channel
    (Společnost pro radioelektronické inženýrství, 2006-12) Jeong, Kilsoo; Yokoyama, Mitsuo; Uehara, Hideyuki
    In this paper, we propose a robust adaptive minimum mean square error (MMSE) Rake receiver for asynchronous DS-CDMA systems. The receiver uses the modified MMSE criterion that incorporates the differential detection and the amplitude compensation for interference cancellation in a time-varying multipath fading channel. We investigate that the proposed Rake receiver can achieve the higher output signal to interference plus noise ratio (SINR) than the conventional adaptive Rake receiver, since the modified MMSE criterion does not attempt to track the time-varying MMSE solution. Computer simulations verify that the performance of the proposed Rake receiver is better than those of the conventional and the adaptive Rake receiver.