2006/4

Browse

Recent Submissions

Now showing 1 - 5 of 16
  • Thumbnail Image
    Item
    Synthesis of New Biquad Filters Using Two CFOAs
    (Společnost pro radioelektronické inženýrství, 2006-12) Vochyan, Josef
    This paper deals with synthesis based on new autonomous circuit using two current feedback operational amplifiers. Four possible second-order structures are derived and several active RC filters are described. One new circuit of the band-pass filter is introduced in detail. Its parameters are studied symbolically, tested by simulations and confirmed by measurements.
  • Thumbnail Image
    Item
    Problem of Bundled Two-Wire Cable of Tested Equipment in Emission Measurement
    (Společnost pro radioelektronické inženýrství, 2006-12) Bittera, Miki; Smiesko, Viktor; Kovac, Karol
    Many factors that influence radiated emission measurement exist. Except of factors relative to measuring chain \"test site - antenna - receiver\" there are some factors caused by operating personnel like inappropriate configuration of tested equipment, etc. Tested equipments contain generally attached cables of different length; the longer ones shall be shortened by folding into a bundle. The aim of this paper is to analyze the behavior of such cables and its influence on results of radiated emission measurement.
  • Thumbnail Image
    Item
    Multireflector Antennas - Cascaded Structures with Frequency Selective Surfaces
    (Společnost pro radioelektronické inženýrství, 2006-12) Hertl, Ivo; Raida, Zbynek; Novacek, Zdenek
    The problem of increasing the gain of directional multiband antennas is solved in the paper. A single-fed multiband (wideband) planar dipole is combined with cascaded (sandwiched) reflectors made of frequency selective surfaces. Each of those reflectors is placed in a quarter-wavelength distance from the dipole at the frequency of operation. The impedance matching is particularly achieved by active element properties, and impedance symmetrization. Further transformation is made by a planar circuit, placed on the active element plane. The antenna gain is set by the reflector elements amount (reflector plane dimensions). The antenna structure enables its setting into arrays with in-phase feeding.
  • Thumbnail Image
    Item
    Estimation of Radiated Fields of Small Horizontal Submodules Based on a Lumped-Element Model
    (Společnost pro radioelektronické inženýrství, 2006-12) Valek, Martin; Leone, Marco
    A novel approach to the estimation of radiated electric field of small horizontal submodules is presented. The principle idea is to describe the radiating submodule-on-motherboard structure with a lumped-element equivalent circuit which includes both the geometrical and the electrical parameters. The electromagnetic emission from the structure is approximated by the radiation characteristics of a Hertzian dipole driven by the antenna voltage resulting from the connector equivalent circuit. Therefore, no time consuming numerical field simulations are needed to evaluate the radiated electric field. Instead, a fast frequency circuit analysis with e.g. PSPICE is sufficient. Moreover, this modeling approach provides a clear insight concerning the influence of geometrical and electrical parameters with respect to radiated emissions. Finally, the computational solutions are compared with experimental results, demonstrating a good correspondence regarding engineering purposes.
  • Thumbnail Image
    Item
    Electromagnetic Compatibility of Matrix Converter System
    (Společnost pro radioelektronické inženýrství, 2006-12) Lettl, Jiri; Fligl, Stanislav
    The presented paper deals with matrix converters pulse width modulation strategies design with emphasis on the electromagnetic compatibility. Matrix converters provide an all-silicon solution to the problem of converting AC power from one frequency to another, offering almost all the features required of an ideal static frequency changer. They possess many advantages compared to the conventional voltage or current source inverters. A matrix converter does not require energy storage components as a bulky capacitor or an inductance in the DC-link, and enables the bi-directional power flow between the power supply and load. The most of the contemporary modulation strategies are able to provide practically sinusoidal waveforms of the input and output currents with negligible low order harmonics, and to control the input displacement factor. The perspective of matrix converters regarding EMC in comparison with other types of converters is brightly evident because it is no need to use any equipment for power factor correction and current and voltage harmonics reduction. Such converter with proper control is properly compatible both with the supply mains and with the supplied load. A special digital control system was developed for the realized experimental test bed which makes it possible to achieve greater throughput of the digital control system and its variability.