Various Order Low–Pass Filter with the Electronic Change of Its Approximation

A design of a low pass frequency filter with the electronic change of the approximation characteristics of resulting responses is presented. The filter also offers the reconnection–less reconfiguration of the order (1st, 2nd, 3rd and 4th order functions are available). Furthermore, the filter offers the electronic control of the cut–off frequency of the output response. The feature of the electronic change of the approximation characteristics has been investigated for Butterworth, Bessel, Cauer, Chebyshev and Inverse Chebyshev approximations. The design is verified by PSpice simulations and experimental measurements. The results are also supported by the transient domain response (response to the square waveform), comparison of group delay, sensitivity analysis and implementation feasibility based on given approximation. The benefit of the proposed electronic change of the approximation characteristics feature (in general signal processing or for sensors in particular) has been presented and discussed for an exemplary scenario

Analog Implementation of Fractional-Order Elements and Their Applications

With advancements in the theory of fractional calculus and also with widespread engineering application of fractional-order systems, analog implementation of fractional-order integrators and differentiators have received considerable attention. This is due to the fact that this powerful mathematical tool allows us to describe and model a real-world phenomenon more accurately than via classical “integer” methods. Moreover, their additional degree of freedom allows researchers to design accurate and more robust systems that would be impractical or impossible to implement with conventional capacitors. Throughout this thesis, a wide range of problems associated with analog circuit design of fractional-order systems are covered: passive component optimization of resistive-capacitive and resistive-inductive type fractional-order elements, realization of active fractional-order capacitors (FOCs), analog implementation of fractional-order integrators, robust fractional-order proportional-integral control design, investigation of different materials for FOC fabrication having ultra-wide frequency band, low phase error, possible low- and high-frequency realization of fractional-order oscillators in analog domain, mathematical and experimental study of solid-state FOCs in series-, parallel- and interconnected circuit networks. Consequently, the proposed approaches in this thesis are important considerations in beyond the future studies of fractional dynamic systems

NASA Tech Briefs, March 1992

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