2007/3

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    Examination of Newton's Method Used for Indirect Frequency Offset Estimation
    (Společnost pro radioelektronické inženýrství, 2007-09) Dzubera, Jakub
    This paper deals with the topic of an indirect carrier frequency offset estimation and elimination. The main goal is to modify a conventional method as an attempt to develop a different approach and then to compare the performance of the modified method with the performance of the conventional one. The conventional approach is here represented by the gradient optimization method called the steepest descent. It is the base for the modification which utilizes Newton\'s method for the indirect carrier offset estimation. Both algorithms are implemented as phase-locked loops in a model of communication system. The simulation is processed in Matlab.
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    Efficient Architecture and Implementation of Vector Median Filter in Co-Design Context
    (Společnost pro radioelektronické inženýrství, 2007-09) Boudabous, Anis; Khriji, Lazhar; Ben Atitallah, A.; Kadionik, P.; Masmoudi, Nouri
    This work presents an efficient fast parallel architecture of the Vector Median Filter (VMF) using combined hardware/software (HW/SW) implementation. The hardware part of the system is implemented using VHDL language, whereas the software part is developed using C/C++ language. The software part of the embedded system uses the NIOS-II softcore processor and the operating system used is μClinux. The comparison between the software and HW/SW solutions shows that adding a hardware part in the design attempts to speed up the filtering process compared to the software solution. This efficient embedded system implementation can perform well in several image processing applications.
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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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    Iterative Unsupervised GMM Training for Speaker Indexing
    (Společnost pro radioelektronické inženýrství, 2007-09) Paralic, Martin; Jarina, Roman
    The paper addresses a novel algorithm for speaker searching and indexation based on unsupervised GMM training. The proposed method doesn\'t require a predefined set of generic background models, and the GMM speaker models are trained only from test samples. The constrain of the method is that the number of the speakers has to be known in advance. The results of initial experiments show that the proposed training method enables to create precise GMM speaker models from only a small amount of training data.
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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.