2007/3

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    Spreading Sequences Generated Using Asymmetrical Integer-Number Maps
    (Společnost pro radioelektronické inženýrství, 2007-09) Sebesta, Vladimir
    Chaotic sequences produced by piecewise linear maps can be transformed to binary sequences. The binary sequences are optimal for the asynchronous DS/CDMA systems in case of certain shapes of the maps. This paper is devoted to the one-to-one integer-number maps derived from the suitable asymmetrical piecewise linear maps. Such maps give periodic integer-number sequences, which can be transformed to the binary sequences. The binary sequences produced via proposed modified integer-number maps are perfectly balanced and embody good autocorrelation and crosscorrelation properties. The number of different binary sequences is sizable. The sequences are suitable as spreading sequences in DS/CDMA systems.
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    Biquads Based on Single Negative Impedance Converter Implemented by Classical Current Conveyor
    (Společnost pro radioelektronické inženýrství, 2007-09) Dostal, Tomas; Axman, Vladimir
    The paper deals with continuous-time ARC biquadratic (second-order) filters based on the single classical three-port current conveyors, so called second generation CC II. A unique application of the CC II is discussed, when the terminals Y and Z are connected together. Using this way a negative impedance converter is obtained as a suitable building block in synthesis of several biquads, including notch filters.
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    New Statistics for Texture Classification Based on Gabor Filters
    (Společnost pro radioelektronické inženýrství, 2007-09) Bandzi, Peter; Oravec, Milos; Pavlovicova, Jarmila
    The paper introduces a new method of texture segmentation efficiency evaluation. One of the well known texture segmentation methods is based on Gabor filters because of their orientation and spatial frequency character. Several statistics are used to extract more information from results obtained by Gabor filtering. Big amount of input parameters causes a wide set of results which need to be evaluated. The evaluation method is based on the normal distributions Gaussian curves intersection assessment and provides a new point of view to the segmentation method selection.
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    Analysis of Analog Neural Network Model with CMOS Multipliers
    (Společnost pro radioelektronické inženýrství, 2007-09) Docheva, Liliana; Bekiarski, Alexander; Dochev, Ivo
    The analog neural networks have some very useful advantages in comparison with digital neural network, but recent implementation of discrete elements gives not the possibility for realizing completely these advantages. The reason of this is the great variations of discrete semiconductors characteristics. The VLSI implementation of neural network algorithm is a new direction of analog neural network developments and applications. Analog design can be very difficult because of need to compensate the variations in manufacturing, in temperature, etc. It is necessary to study the characteristics and effectiveness of this implementation. In this article the parameter variation influence over analog neural network behavior has been investigated.
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    A Robust Chaos-Based True Random Number Generator Embedded in Reconfigurable Switched-Capacitor Hardware
    (Společnost pro radioelektronické inženýrství, 2007-09) Drutarovsky, Milos; Galajda, Pavol
    This paper presents a new chaos-based True Random Number Generator (TRNG) with a decreased voltage supply sensitivity. Contrary to the traditionally used sources of randomness it uses a well-defined deterministic switched-capacitor circuit that exhibits chaos. The whole design is embedded into a commercially available mixed-signal Cypress PSoC reconfigurable device without any external components. The proposed design is optimized for a reduction of influence of the supply voltage to the quality of the generated random bit stream. The influence of circuit non-idealities is significantly reduced by the proposed XOR corrector and optimized circuit topology. The ultimate output bit rate of the proposed TRNG is 60 kbit/s and the quality of generated bit-streams is confirmed by passing standard FIPS and correlation statistical tests performed in the full range of PSoC device supply voltages.