2010/3

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    BER Performance Simulation of Generalized MC DS-CDMA System with Time-Limited Blackman Chip Waveform
    (Společnost pro radioelektronické inženýrství, 2010-09) Develi, Ibrahim; Kockaya, Kenan
    Multiple access interference encountered in multicarrier direct sequence-code division multiple access (MC DS-CDMA) is the most important difficulty that depends mainly on the correlation properties of the spreading sequences as well as the shape of the chip waveforms employed. In this paper, bit error rate (BER) performance of the generalized MC DS-CDMA system that employs time-limited Blackman chip waveform is presented for Nakagami-m fading channels. Simulation results show that the use of Blackman chip waveform can improve the BER performance of the generalized MC DS-CDMA system, as compared to the performances achieved by using timelimited chip waveforms in the literature.
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    A Novel Bandpass Filter Using a Combination of Open-Loop Defected Ground Structure and Half-Wavelength Microstrip Resonators
    (Společnost pro radioelektronické inženýrství, 2010-09) Vagner, Petr; Kasal, Miroslav
    This paper deals with a defected ground structure (DGS) open-loop resonator analysis and bandpass filter design, using coupled DGS and microstrip resonators. The combination of DGS and microstrip resonators allows using top and bottom sides of the microwave substrate, therefore the resonators can partially overlap and a desired coupling coefficient can be easily achieved. The open-loop DGS resonator properties are investigated, as well as coupling types between the resonators. Finally, two bandpass filters are designed and simulated. The sixth order filter is fabricated and the results are compared with measurement. The introduced structure represents an alternative to a conventional parallel-coupled half wavelength microstrip resonator bandpass filter.
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    Admission Control Techniques for UMTS System
    (Společnost pro radioelektronické inženýrství, 2010-09) Kejik, Petr; Hanus, Stanislav
    Universal mobile telecommunications system (UMTS) is one of the 3rd generation (3G) cell phone technologies. The capacity of UMTS is interference limited. Radio resources management (RRM) functions are therefore used. They are responsible for supplying optimum coverage, ensuring efficient use of physical resources, and providing the maximum planned capacity. This paper deals with admission control techniques for UMTS. An own UMTS simulation program and several versions of proposed admission control algorithms are presented in this paper. These algorithms are based on fuzzy logic and genetic algorithms. The performance of algorithms is verified via simulations.
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    Ternary Chaotic Pulse Compression Sequences
    (Společnost pro radioelektronické inženýrství, 2010-09) Seventline, J. B.; Rani, D. Elizabath; Rajeswari, K. Raja
    In this paper method available for generating ternary sequences is discussed. These sequences are useful in many applications but specifically in synchronization of block codes and pulse compression in radar. The ternary sequences are derived from chaotic maps. It is feasible to achieve simultaneously superior performances in detection range and range resolution using the proposed ternary sequences. The properties of these sequences like autocorrelation function, Peak Side Lobe Ratio (PSLR), ambiguity diagram and performance under AWGN noise background has been studied. The generation of these sequences is much simpler, and the available number of sequences is virtually infinite and not limited by the length of the sequence.
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    A Novel Current-Mode Full-Wave Rectifier Based on One CDTA and Two Diodes
    (Společnost pro radioelektronické inženýrství, 2010-09) Khateb, Fabian; Vavra, Jiri; Biolek, Dalibor
    Precision rectifiers are important building blocks for analog signal processing. The traditional approach based on diodes and operational amplifiers (OpAmps) exhibits undesirable effects caused by limited OpAmp slew rate and diode commutations. In the paper, a full-wave rectifier based on one CDTA and two Schottky diodes is presented. The PSpice simulation results are included.