A design algorithm for constrained equiripple digital filters

The large scale integration (LSI) of systems imposes several new requirements on a digital filter. Typically, these requirements can be met by designing equiripple filters with arbitrary passband or stop-band shaping, with prescribed zeros or poles, and with different, both in number and magnitude, ripples in passband and stopband. The design of such filters requires constrained equiripple approximation of an arbitrary function. The approximation is carried out by employing the analytical scheme developed for design of elliptical recursive filters and by treating the arbitrary function as perturbed zero function which is defined over two disjoint intervals. The efficacy of this scheme is illustrated with designs of passband-shaped and stopband-shaped low-pass digital filters.