2008/4

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    Design of Microstrip Band Pass Fractal Filter for Suppression of Spurious Band
    (Společnost pro radioelektronické inženýrství, 2008-12) Baral, R. N.; Singhal, P. K.
    In this paper, the design and subsequent fabrication of a hairpin-line band pass filter has been proposed. This filter exhibits periodic frequency response. By proper design, the spurious bands are being suppressed significantly through the implementation of Koch fractal on the microstrip coupled line.
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    Shielding Effectiveness of Laminated Shields
    (Společnost pro radioelektronické inženýrství, 2008-12) Jayasree, P. V. Y.; Baba, V. S. S. N. Srinivasa; Rao, B. Prabhakara
    Shielding prevents coupling of undesired radiated electromagnetic energy into equipment otherwise susceptible to it. In view of this, some studies on shielding effectiveness of laminated shields with conductors and conductive polymers using plane-wave theory are carried out in this paper. The plane wave shielding effectiveness of new combination of these materials is evaluated as a function of frequency and thickness of material. Conductivity of the polymers, measured in previous investigations by the cavity perturbation technique, is used to compute the overall reflection and transmission coefficients of single and multiple layers of the polymers. With recent advances in synthesizing stable highly conductive polymers these lightweight mechanically strong materials appear to be viable alternatives to metals for EM1 shielding.
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    A New CAC Method Using Queuing Theory
    (Společnost pro radioelektronické inženýrství, 2008-12) Baronak, Ivan; Kvackaj, Peter
    The CAC (Connection Admission Control) method plays an important role in the ATM (Asynchronous Transfer Mode) network environment. The CAC is the first step in the prevention of congested states in the network topology, and conducts to the optimal network resources utilization. The paper is aimed to propose an enhancement for a convolution method that is one of the statistical CAC methods used in ATM. The convolution method uses a buffer-less assumption in the estimation of the cell loss. Using formulas for the G/M/1 queuing system, the cell loss can be estimated as the buffer overflow probability. In this paper, the proposed CAC method is compared with other three statistical CAC methods, and conclusions regarding the exploitation of the CAC method are presented
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    Slotted PIFA for Mobile Communication Devices
    (Společnost pro radioelektronické inženýrství, 2008-12) Bonefacic, Davor; Rapinac, Bojan; Bartolic, Juraj
    Slotted PIFA with capacitive loading for operation in the 880 / 960 MHz band is presented. The PIFA is intended for mobile terminals in GSM mobile communication network. The antenna is placed on a ground plane with dimensions of an average handheld device. It is optimized by using electromagnetic simulator and a prototype is manufactured. Calculated and measured results agree very well. Input impedance matching with SWR < 3 in the whole band was achieved. Maximum gain of 3.2 dBi is measured. Preliminary studies of the influence of the user\'s head and hand on the antenna characteristics have been performed.
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    Utilization of Faraday Mirror in Fiber Optic Current Sensors
    (Společnost pro radioelektronické inženýrství, 2008-12) Drexler, Petr; Fiala, Pavel
    Fiber optic sensors dispose of some advantages in the field of electrical current and magnetic field measurement, like large bandwidth, linearity, light transmission possibilities. Unfortunately, they suffer from some parasitic phenomena. The crucial issue is the presence of induced and latent linear birefringence, which is imposed by the fiber manufacture imperfections as well as mechanical stress by fiber bending. In order to the linear birefringence compensation a promising method was chosen for pulsed current sensor design. The method employs orthogonal polarization conjugation by the back direction propagation of the light wave in the fiber. The Jones calculus analysis presents its propriety. An experimental fiber optic current sensor has been designed and realized. The advantage of the proposed method was proved considering to the sensitivity improvement.