2008/4

Browse

Recent Submissions

Now showing 1 - 5 of 33
  • Thumbnail Image
    Item
    A New Application of Current Conveyors: The Design of Wideband Controllable Low-Noise Amplifiers
    (Společnost pro radioelektronické inženýrství, 2008-12) Godara, Balwant; Fabre, Alain
    The aim of this paper is three-fold. First, it reviews the low-noise amplifier and its relevance in wireless communications receivers. Then it presents an exhaustive review of the existing topologies. Finally, it introduces a new class of LNAs, based on current conveyors, describing the founding principle and the performances of a new single-ended LNA. The new LNAs offer the following notable advantages: total absence of passive elements (and the smallest LNAs in their respective classes); wideband performance, with stable frequency responses from 0 to 3 GHz; easy gain control over wide ranges (0 to 20 dB). Comparisons with other topologies prove that the new class of LNA greatly advances the state of the art.
  • Thumbnail Image
    Item
    Synthesizing Sierpinski Antenna by Genetic Algorithm and Swarm Optimization
    (Společnost pro radioelektronické inženýrství, 2008-12) Vidal, Beatriz Maria; Raida, Zbynek
    The paper discusses the synthesis of the Sierpinski antenna operating at three prescribed frequencies: 0.9 GHz, 1.8 GHz (both GSM) and 2.4 GHz (Bluetooth). In order to synthesize the antenna, a genetic algorithm and a particle swarm optimization were used. The numerical model of the antenna was developed in Zeland IE3D, optimization scripts were programmed in MATLAB. Results of both the optimization methods are compared and experimentally verified.
  • Thumbnail Image
    Item
    ACE Strategy with Virtual Channels
    (Společnost pro radioelektronické inženýrství, 2008-12) Vondrasek, Martin; Sovka, Pavel; Tichy, Tomas
    Cochlear implant is an electronic device, which can mediate hearing sensations to profoundly deaf people. Contemporary cochlear implants are sophisticated electronic devices; however, their performance could still be improved. This paper describes an experiment we made in that direction: additional 21 virtual channels were implemented by sequential stimulation of adjacent intracochlear electrodes, and the ACE strategy with virtual channels (ACEv, Advanced Combination Encoder strategy with virtual channels) for the Nucleus® 24 Cochlear Implant System was created and verified in a clinical test with four patients.
  • Thumbnail Image
    Item
    Numerical Modeling of Magnetic Field Deformation as Related to Susceptibility Measured with an MR System
    (Společnost pro radioelektronické inženýrství, 2008-12) Bartusek, Karel; Fiala, Pavel; Mikulka, Jan
    The possibility is studied of numerical modeling of magnetic field deformations in the environment of measured diamagnetic and paramagnetic samples for the purposes of studying magnetic resonance (MR) image deformations owing to the susceptibility of heterogeneous materials (objects). The verification was realized using a simple sample configuration (circular plate), and the numerically modeled cross-sections were compared with the experimentally obtained values of the magnetic field measured by the MR gradient echo technology. The results show that it is possible – via a technical calculation – to determine a magnetic field deformation in the environment of complex-shaped or non-homogeneous structures in the MR experiments.
  • Thumbnail Image
    Item
    Parametric Study of Mushroom-like and Planar Periodic Structures in Terms of Simultaneous AMC and EBG Properties
    (Společnost pro radioelektronické inženýrství, 2008-12) Kovacs, Peter; Raida, Zbynek; Martinez-Vazquez, Marta
    In the paper, the parametric analysis of a mushroom-like and a planar metallo-dielectric periodic structure with square unit cell and metallic patch is presented. First, the angular stability for different unit cell settings was studied. Second, restrictions for simultaneous behavior as artificial magnetic conductor (AMC) and electromagnetic band gap (EBG) are briefly discussed. Finally, main differences between the mushroom-like and the planar structure are specified and conclusions are formulated.