MATLAB based analog filter design

Abstract

The goal of this work is to show a software package, based in Matlab, that simplifies the process of designing analog filters. This package is menu-oriented using the Matlab capabilities for doing so. The package is able to design lowpass, highpass, bandpass and bandreject filters. The approximation magnitude responses can be Butterworth (maximally flat magnitude), Chebyshev (equal-ripple), inverse Chebyshevi and elliptic. In the case of phase response, there is also the Thomson (maximally flat delay) also known as the Bessel response. The output for the approximation stage is a set of data that includes the transfer function poles and zeros, quadratic factors for both numerator and denominator polynomials, and the numerator and denominator polynomials. The network realizations can be either passive or active realizations. For the passive realizations, low sensitivity ladder realization is used. This realization is available for any approximation type. In the case of the active realizations, the authors have implemented the cascade of biquad stages but they are working on the active ladder realization. For the biquad stages, the Sallen-Key realization, multiple feedback, state-variable KHN, state variable Tow-Thomas and the GIC based biquad are available.