Implementation of fractional-order filters using curve-fitting based frequency response approximation techniques
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Date
2023-02-17
Authors
Νάκο, Τζούλια
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Abstract
The subject of this M.Sc. Thesis is the implementation of fractional-order filters using a curve-fitting based magnitude response approximation technique. This is an innovative method, where the frequency characteristics of the fractional filters, including order, type and cut-off frequency are fully controlled by the designer.
The first step of this study, is the employment of suitable commands of the MATLAB software, which lead to a rational integer-order transfer function, which approximates the magnitude response of the filter. These transfer functions are implemented in two different ways, where both of them offer versatile structures in the sense that they are capable of implementing several types of filters with various characteristics without altering the core of the structure.
The electronically controlled implementation is realized by a 4th-order IFLF topology implemented by a OTA-C structure, which offers electronic tuning of the filters’ characteristics. The performance of the proposed structure is verified through post-layout simulations using Cadence and the Design Kit provided by the Austria Mikro Systems (AMS) 0.35µm CMOS technology process.
The digitally controlled implementation is realized by a 4th-order FLF structure employing the Field-Programmable Analog Array (FPAA) AN231E04 device provided by Anadigm, which offers design flexibility and versatility. The obtained experimental results, also confirm the performance of the presented method.
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Keywords
Fractional calculus, Fractional-order circuits, Fractional-order elements, Fractional-order filters, CMOS integrated circuits, Operational transconductance amplifiers, Field-programmable analog arrays