2008/1

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    Recognition of OFDM Modulation Method
    (Společnost pro radioelektronické inženýrství, 2008-04) Ulovec, Karel
    This contribution deals with asynchronous noncoherent recognition of modulation types. The main aim is to recognize OFDM modulation method from some other single-carrier analog and digital modulation types in the presence of AWGN noise. The described solution of recognizer uses key features of the received signal. The signal amplitude is observed at the output of the quadrature intermediate-frequency stage. The properties of the recognizer are verified by simulations using Matlab.
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    Design of Primary Feeds for 32m KDDI Antenna System IBA-4 in Cassegrain Configuration
    (Společnost pro radioelektronické inženýrství, 2008-04) Galuscak, Rastislav; Watanabe, Michiaki; Hazdra, Pavel; Takeda, Shigeru; Seki, Kouichi; Prochazka, Miroslav; Uchiyama, Yoosuke
    Physically large dimensional dish antennas in Cassegrain configuration have played an important role in satellite communications during the past several decades. Recently, however, emerging new technologies have begun to displace these elegant antennas in professional telecommunication service due to their lower operating costs. A beneficial aspect of this transitional situation is that it has created opportunities for amateur radio enthusiasts to use these soon-to-be-retired dish antenna systems for limited experimental testing. Adaptation of these professionally designed antennas to bands allocated for amateur radio service presents excellent educational opportunities in using antenna engineering skills and the use of modern electromagnetic simulation software provides a novel perspective for these antenna design and transformation tasks.
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    Time-Frequency Decomposition of an Ultrashort Pulse: Wavelet Decomposition
    (Společnost pro radioelektronické inženýrství, 2008-04) Khelladi, Mounir; Seddiki, Omar; Bendimerad, Fethi Tarik
    An efficient numerical algorithm is presented for the numerical modeling of the propagation of ultrashort pulses with arbitrary temporal and frequency characteristics through linear homogeneous dielectrics. The consequences of proper sampling of the spectral phase in pulse propagation and its influence on the efficiency of computation are discussed in detail. The numerical simulation presented here is capable of analyzing the pulse in the temporal-frequency domain. As an example, pulse propagation effects such as temporal and spectral shifts, pulse broadening effects, asymmetry and chirping in dispersive media are demonstrated for wavelet decomposition.
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    Broadband Measurement of Complex Permittivity Using Reflection Method and Coaxial Probes
    (Společnost pro radioelektronické inženýrství, 2008-04) Zajicek, Radim; Oppl, Ladislav; Vrba, Jan
    This paper describes and evaluates a method for determining complex permittivity, and presents results of permittivity measurement of some substances. Complex permittivity of a phantom of biological muscle tissue, of some industrial chemicals and dielectrics is found. A non-destructive and non-invasive method based on reflection coefficient measurement of an open-ended coaxial line attaching the material under test is used. Two coaxial probes are under investigation. Vector measurement of the reflection coefficient on the interface between probes and measured samples is performed with the aid of network analyzer in the frequency range from 300 kHz to 3 GHz. Numerical modeling (FDTD) is compared with measurement. The results indicate that using the coaxial probe with dimensions of N connector the method is suitable in the frequency range approximately from 30 MHz to 1 GHz and using the probe with dimensions of SMA connector in range approximately from 30 MHz to 3 GHz.
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    Planar Tri-Band Antenna Design
    (Společnost pro radioelektronické inženýrství, 2008-04) Pokorny, Michal; Horak, Jiri; Raida, Zbynek
    The paper briefly uncovers techniques used for a design of compact planar antennas in order to achieve the wideband and the multi-band capability. The main topic is aimed to the multi-objective optimization using genetic algorithms. A quarter-wavelength planar inverted-F antenna (PIFA) using a slot and shorted parasitic patches is chosen to cover GSM900, GSM1800 and ISM2400 bands. A global multi-objective optimization uses a binary genetic algorithm with a composite objective function to tune this antenna. The impedance match and the direction of maximum gain are desired parameters to improve.