2004/2

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Recent Submissions

Now showing 1 - 5 of 8
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    On the High Altitude Platform (HAP) W-CDMA System Capacity
    (Společnost pro radioelektronické inženýrství, 2004-06) Taha-Ahmed, Bazil; Calvo-Ramon, Miguel; de Haro-Ariet, Leandro
    The performance of a downlink power control model, based on a n-th power distance law, is evaluated for high altitude platform station (HAPS) W-CDMA systems. The downlink capacity using this model is compared with the uplink capacity. It is shown that the uplink capacity is higher than the downlink capacity.
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    Rain Intensity Statistical Processing and Comparison with ITU-R Recommendations
    (Společnost pro radioelektronické inženýrství, 2004-06) Kvicera, Vaclav; Grabner, Martin; Hlavaty, Michal
    Rain intensities have been measured since February 1992 by means of a heated siphon raingauge. Rain intensity data gathered over 11-year period were statistically processed, cumulative distributions of rain intensities obtained, and relations between them were compared with ITU-R recommendations.
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    S-Parameter Measurements in the Time Domain
    (Společnost pro radioelektronické inženýrství, 2004-06) Tkadlec, Roman
    The paper provides a basic overview of the theory of time-domain measurements. Results of the use time-domain techniques to obtain S-parameter are here presented. Advantages and disadvantages of this technique compared to frequency-domain measurements are mentioned.
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    Nonlinear Resistor with Polynomial AV Characteristics and Its Application in Chaotic Oscillator
    (Společnost pro radioelektronické inženýrství, 2004-06) Petrzela, Jiri; Pospisil, Vaclav
    This paper shows the realization of two terminal devices with an arbitrary polynomial nonlinearity up to the fifth order. The proposed design procedure is completely systematic using minimum of components. The very heart of our conception is four-channel four-quadrant analog multiplier MLT04. The implementation of synthesized nonlinear resistor as a general nonlinearity in chaotic oscillator is also presented and experimentally verified.
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    Modeling Broadband Microwave Structures by Artificial Neural Networks
    (Společnost pro radioelektronické inženýrství, 2004-06) Raida, Zbynek; Lukes, Zbynek; Otevrel, Viktor
    The paper describes the exploitation of feed-forward neural networks and recurrent neural networks for replacing full-wave numerical models of microwave structures in complex microwave design tools. Building a neural model, attention is turned to the modeling accuracy and to the efficiency of building a model. Dealing with the accuracy, we describe a method of increasing it by successive completing a training set. Neural models are mutually compared in order to highlight their advantages and disadvantages. As a reference model for comparisons, approximations based on standard cubic splines are used. Neural models are used to replace both the time-domain numeric models and the frequency-domain ones.