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Author: search.filters.author.Langhammer, LukasSubject: search.filters.subject.Fractional-order

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    Integer- And fractional-order VCO using non-inertial amplitude stabilization and modern active elements
    (2020-04-28)
    Sotner, Roman
    ;
    Petrzela, Jiri
    ;
    Jerabek, Jan
    ;
    Langhammer, Lukas
    ;
    Polak, Josef
    This paper introduces design of the linearly tunable quadrature voltage-controlled oscillator (VCO) using modern off-the-shelf active elements suitable for the design of electronically adjustable applications. The simplified topology was achieved using non-inertial stabilization of amplitude. It allows targeting adjustability of the oscillation frequency only into lossless integrator part of the topology. This arrangement simplifies the design and the tenability also. Derived symbolical expressions indicate that gain adjustment of used amplifiers (that are still in single path) does not influence amplitude and phase shift ratio of generated waveforms, which is a beneficial feature. The performances of the circuit are tested experimentally in band of units of MHz and results confirmed expected behavior. Initial study of the oscillator with fractional-order capacitors is presented and discussed. Results are supported by laboratory measurements.
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    Operational frequency bandwidth rescalable implementations of constant phase devices
    (2019-04-01)
    Sotner, Roman
    ;
    Jerabek, Jan
    ;
    Langhammer, Lukas
    ;
    Polak, Ladislav
    ;
    Jaikla, Winai
    This paper presents and verifies a method for rescalability of operational bandwidth in constant phase devices (two-port elements, two-port transfer blocks). Most importantly, in comparison with a standard approach, it allows to utilize suitable values of capacitance in the case of operation at low-frequency bands. The capacitance multipliers based on a controllable variable gain amplifier are implemented in examples of simple fractional-order systems (two-port integrators). These examples consist of novel bilinear immittances with independently settable zero and pole frequency coordinates, based on widespread commercially available current conveyors of second generation. The capacitance multiplier extends features of the bilinear immittance and full implementation of the system. PSpice simulations, using off-the-shelf elements, confirm operability of the proposed concept.