1999/1

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    Exploration of Neural Networks in the Design of Microwave Structures
    (Společnost pro radioelektronické inženýrství, 1999-04) Z. Raida
    Artificial neural networks can be used for modeling microwave structures in order to obtain computationally efficient models of investigated systems. In conjunction with proper optimization techniques, these neural models can be explored for an efficient full-wave design of microwave structures. Moreover, neural networks can serve as a direct design tool of microwave systems. In this paper, an overview of the so-far published applications of neural networks in microwaves is presented and their exploration in the full-wave design is discussed. Described neural modeling and design is illustrated by modeling and design of frequency-selective surfaces.
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    High Frequency Components Recovery in Music Signals
    (Společnost pro radioelektronické inženýrství, 1999-04) Brejl, M.; Sebesta, V.
    A new technique is presented which improves the subjective quality of band-limited music by recovery of high frequency components. Sequences of harmonics are found in the band-limited signal and these sequences are expanded to the high frequency band to estimate the lost part of spectrum. High frequency signal is generated to match this estimation and is added to the band-limited signal.
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    Network Communication by Optical Directional Link
    (Společnost pro radioelektronické inženýrství, 1999-04) Wilfert, O.; Biolková, Viera
    In this article, infrared point-to-point technologies (optical directional links) are discussed which are designed for digital transmissions. Optical directional links (ODLs) are transparent for the SDH/ATM, FDDI-II, Ethernet, and Token Ring protocols. Depending on type, ODL ranges are 300 m, 500 m, 1000 m and 2000 m. Steady and statistical models of ODL are presented as well as the measuring ODL arrangement and the graphs concerning the fluctuations of the received signal.
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    ARC Filters Using Only Followers
    (Společnost pro radioelektronické inženýrství, 1999-04) Dostal, T.
    Several structures of the active RC filters using non-inverting voltage unity-gain followers and dual current positive followers are given in this paper. These structures can be suitable implemented by the positive second generation current conveyors or by the transimpedance operational amplifiers. A symbolical analysis using SNAP and a simulation by PSpice have been made to confirm the given theoretical approach.
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    Automatically Derived Units in the Speech Processing
    (Společnost pro radioelektronické inženýrství, 1999-04) Cernocky, J.
    Current systems for recognition, synthesis, very low bit-rate (VLBR) coding and text-independent speaker verification rely on sub-word units determined using phonetic knowledge. This paper presents an alternative to this approach - determination of speech units using AUSP (Automatic Language Independent Speech Processing) tools. Experimental results for speaker-dependent VLBR coding are reported on two databases: average rate of 120 bps for unit encoding was achieved. In verification, this approach was tested during 1998's NIST-NSA evaluation campaign with a MLP-based scoring system.