2006/3

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    Design of Dual Bandpass and Bandreject LC Ladder Filters
    (Společnost pro radioelektronické inženýrství, 2006-09) Bicak, Jan; Hospodka, Jir
    This paper deals with the design of two-passband bandpass and two-stopband bandreject LC ladder filters. The design method is based on the special dual frequency transformation that transforms normalized lowpass to either bandpass with two passbands or to bandreject with two stopbands that are specified by four cutoff frequencies. The paper shows analytical solution relating these four cutoff frequencies to parameters of dual frequency transformation. It enables a direct computation of dual band LC filter elements from a normalized lowpass filter by means of simple relations. These relations have been implemented in the mathematical program Maple (TM) as new user functions. They are supposed to be used as an enhancement of Syntfil package which is intended for analog filter design in program Maple. Specific application is shown on an example of the two-passband bandpass LC filter design.
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    Optimization of Dynamic Range of Cascade Filter Realization
    (Společnost pro radioelektronické inženýrství, 2006-09) Hospodka, Jiri
    This paper deals with a dynamic range optimization procedure for active filters based on the cascade realization. Dynamic characteristics of the cascade filter depend on many factors, mainly on pole-zero pairing, section ordering and gain assignment. Just the procedure for an optimal gain assignment for particular biquadratic sections is discussed in this paper. The input parameters of the procedure are parameters of particular biquads i.e. pole frequency ω0, quality factor Q, eventually zero frequency ωn for elliptic section and the transfer function type of the section. The gain is distributed so that output signal limitation of particular biquads occurs for the same level of the filter input signal. The procedure is versatile - can be used for analog as well as for digital filters with the cascade structure. The presented algorithm is fully universal (does not suppose any simplification). It has been used in Syntfil package for the filter design in the mathematical program Maple.
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    Influence of the FEC Channel Coding on Error Rates and Picture Quality in DVB Baseband Transmission
    (Společnost pro radioelektronické inženýrství, 2006-09) Kratochvil, Tomas
    The paper deals with the component analysis of DTV (Digital Television) and DVB (Digital Video Broadcasting) baseband channel coding. Used FEC (Forward Error Correction) error-protection codes principles are shortly outlined and the simulation model applied in Matlab is presented. Results of achieved bit and symbol error rates and corresponding picture quality evaluation analysis are presented, including the evaluation of influence of the channel coding on transmitted RGB images and their noise rates related to MOS (Mean Opinion Score). Conclusion of the paper contains comparison of DVB channel codes efficiency.
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    Controlled Random Search Optimization for Linear Antenna Arrays
    (Společnost pro radioelektronické inženýrství, 2006-09) Merad, Lotfi; Bendimerad, Fethi Tarik; Meriah, Sidi Mohammed
    An optimization problem for designing nonuniformly spaced, linear antenna\'s arrays is formulated and solved by means of a controlled random search algorithm. The proposed iterative method aims at a linear array and the optimization of element positions and excitations coefficients by minimizing the side-lobes level and respecting a beam pattern shape. Selected examples are included, which demonstrate the effectiveness and the design flexibility of the proposed method in the framework of the electromagnetic synthesis of linear antenna arrays.
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    On the Reduced Complexity Interleaving Method for OFDM PAPR Reduction
    (Společnost pro radioelektronické inženýrství, 2006-09) Marsalek, Roman
    Many methods for OFDM Peak to Average Power Ratio reduction have been proposed during approximately last ten years. There are nowadays many research efforts on PAPR reduction methods with reduced computational complexity. The method presented in this paper is based on adaptive symbol selection principle, with several replicas of signal created using set of interleavers incorporated inside an IFFT block at OFDM transmitter. This paper also discusses some practical aspects of this method - influence of zero padding and pilot positions.