2005/3

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    Effective DSP Methods of PSK Feedback Timing Synchronization
    (Společnost pro radioelektronické inženýrství, 2005-09) Sebesta, Jiri; Kasal, Miroslav
    This paper deals with simplification and improvement of data timing synchronization algorithms. Timing error synchronizers are usually the most complicated subsystems in the demodulator, and limit the DSP technique used for the high-rate application. This article is focused on feedback timing estimators for PSK modulation schemes, and shows modifications of widely used algorithms, that are suitable for the DSP implementation, as well as reach better parameters of the detection process. The methods applied in the evaluation of a timing error detector, which is a crucial part of the synchronizer, are described in the last part.
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    All-Pass Filters in Current Mode
    (Společnost pro radioelektronické inženýrství, 2005-09) Dostal, Tomas
    Analogue first, second and high-order all-pass active filters in the current mode, with constant group delay and magnitude responses, are presented in this paper. These filters are based on a modification of the multi-loop feedback canonical structures using signal flow graphs. Implementations by multi-output transconductors, namely classical OTAs and novel CDTAs are given.
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    Simulation of "Tsunami Waves" Propagating along Non-Linear Transmission Lines
    (Společnost pro radioelektronické inženýrství, 2005-09) Valsa, Juraj
    The paper compares three methods for computer simulation of transients on transmission lines with losses and nonlinear behavior, namely distributed LC model, FDTD (Finite-Difference Time-Domain) method, and a new and very effective Method of Slices. The losses are responsible for attenuation and shape changes of the waves as function of time and distance from the source. Special behavior of the line due to voltage-dependent capacitance of the line is considered in detail. The non-linear nature of the line causes that the higher is the voltage the higher is the velocity of propagation. Then, the waves tend to tilt over so that their top moves faster than their base. As a result "tsunami waves" are created on the line. Fundamental algorithms are presented in Matlab language. Several typical situations are solved as an illustration of individual methods.
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    An Efficient Procedure for the Time-Domain Sensitivity Analysis
    (Společnost pro radioelektronické inženýrství, 2005-09) Dobes, Josef
    Standard tools for CAD have limited modes of the sensitivity analysis: PSPICE only contains a static mode and SPECTRE includes frequency-domain and static modes. However, many RF systems use symmetrical structures for enhancing the circuit properties. For such systems, the static sensitivities are zero on principle and hence the time-domain sensitivity analysis should be used. In the paper, a novel recurrent formula for the time/domain sensitivity analysis is derived which uses by-products of an efficient implicit integration algorithm. As the selected integration algorithm is more flexible than the Gear's one that is ordinary used, the sensitivity analysis is more efficient in comparison with the standard CAD tools. An implementation of the method is demonstrated using the analysis of a low-voltage four-quadrant RF multiplier. Nonstandard temperature sensitivity analyses are also tested in the static and dynamic modes.
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    RLS Adaptive Filtering Algorithms Based on Parallel Computations
    (Společnost pro radioelektronické inženýrství, 2005-09) Djigan, Victor I.
    The paper presents a family of the sliding window RLS adaptive filtering algorithms with the regularization of adaptive filter correlation matrix. The algorithms are developed in forms, fitted to the implementation by means of parallel computations. The family includes RLS and fast RLS algorithms based on generalized matrix inversion lemma, fast RLS algorithms based on square root free inverse QR decomposition and linearly constrained RLS algorithms. The considered algorithms are mathematically identical to the appropriate algorithms with sequential computations. The computation procedures of the developed algorithms are presented. The results of the algorithm simulation are presented as well.