2011/1

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    Switched Capacitor Realizations of Fractional-Order Differentiators and Integrators Based on an Operator with Improved Performance
    (Společnost pro radioelektronické inženýrství, 2011-04) Varshney, Pragya; Gupta, Maneesha; Visweswaran, G. S.
    In this paper, switched capacitor realizations of discretized models of half differentiator and half integrator based on a new operator with improved performance have been proposed. This Al-Hsue operator is the weighted sum of the Al-Alaoui operator and the Hsue operator. The discretized models of the Al-Hsue operator have been expanded using Taylor Series Expansion and Continued Fraction Expansion, to be able to develop the Switched Capacitor realizations. These Switched Capacitor realizations are implemented using Spice and the results obtained are compared with the theoretical results of the continuous- time domain half differentiators and integrators. These Spice simulation results are also compared with the results of existing Al-Alaoui operator and Hsue operator based Switched Capacitor realizations of half differentiators and integrators of order 1/2. The results validate the effectiveness of the Switched Capacitor circuit implementation of the proposed approach.
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    Mutual Coupling Between IFF/SSR Microstrip Antennas with Reduced Transversal Size - Experimental Study
    (Společnost pro radioelektronické inženýrství, 2011-04) Sorokosz, Lukasz; Zieniutycz, Wlodzimierz; Pergol, Mariusz; Mazur, Mateusz
    Mutual coupling between IFF/SSR microstrip antennas is investigated experimentally in this paper. At the begining configuration and performance of isolated microstrip antenna fed by H-shaped coupling slot is presented. Next, the vertical and horizontal arrangement of the microstrip antennas array were investigated. The measurements of return loss and coupling coefficients at two operating frequencies for the two orthogonal planes are presented and compared with the results of numerical calculations, showing satisfactory agreement.
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    Insertion Loss Estimation of EMI Filters in Unmatched Input/Output Impedance System
    (Společnost pro radioelektronické inženýrství, 2011-04) Drinovsky, Jiri; Kejik, Zdenek; Ruzek, Vaclav; Zachar, Jiri; Svacina, Jiri
    One of the problems in the design of powerline EMI filters is the uncertainty and ambiguity of their source/load impedances which results in breach of expected filter parameters in a real installation. The paper presents a simple technique for prediction of insertion loss limit values of EMI filters working in arbitrary unmatched mains line impedance systems.
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    Reduction of Sidelobes by Nonuniform Elements Spacing of a Spherical Antenna Array
    (Společnost pro radioelektronické inženýrství, 2011-04) Rupcic, Slavko; Mandric, Vanja; Zagar, Drago
    This paper presents a significant sidelobe reduction if nonuniform elevational spacing of antenna elements on the sphere is used. Antenna elements are progressively phased with a uniform amplitude excitation. The calculation of the required element position is presented. The achieved sidelobe level reduction with unequally spaced arrays could reach even more than 20dB difference with regard to the first significant sidelobe level of equally spaced arrays. By this method, arrays have the ability to produce the desired radiation pattern and could satisfy requirements for many applications.
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    Deriving (MO)(I)CCCII Based Second-order Sinusoidal Oscillators with Non-interactive Tuning Laws using State Variable Method
    (Společnost pro radioelektronické inženýrství, 2011-04) Lahiri, Abhirup
    The paper discusses systematic realization of second-order sinusoidal oscillators using multiple-output second-generation current controlled conveyor (MO-CCCII) and/or its inverting equivalent, namely the multiple-output inverting second-generation current controlled conveyor (MO-ICCCII) by state variable method. State variable method is a powerful technique and has been used extensively in the past to realize active RC oscillators using a variety of active building blocks (ABB). In this work, a noninteractive relationship between the condition of oscillation (CO) and the frequency of oscillation (FO) has been chosen priori and then state variable method is applied to derive the oscillators with grounded capacitors. All the resulting oscillator circuits, eight of them, are “resistor-less”, employ grounded capacitors and do not use more than three (MO)(I)CCCIIs. PSPICE simulation results of a possible CMOS implementation of the oscillators using 0:35μm TSMC CMOS technology parameters have validated their workability.