Filter designer: a complete design and synthesis program for lumped, wave-digital, FIR and IIR filters

Abstract

An interactive filter design program suitable for both experts and non-experts is described. It can be used for the design and synthesis of 64 filter families. These include: lumped, wave-digital (WD) FIR and IIR filters where each may be lowpass, highpass, band rejection, bandpass or phase corrector. Four amplitude approximation functions are available for all these cases; namely Butterworth, Chebyshev, inverse Chebyshev and elliptic approximation functions. Although it operates in both batch and interactive modes, this paper deals exclusively with the interactive mode which is somewhat more general and very easy to use. The filter designer offers superior accuracy and flexibility in manipulating filters with different specifications and network realizations. The synthesized networks are in the form of an LC ladder for lumped filters; lattice and bireciprocal for wave-digital filters: direct form for FIR filters as well as direct, cascade and parallel realizations for IIR filters. Utilities are given for the analysis of the amplitude, phase and group delay for all possible filter designs. In addition, pole-zero patterns and network realization are available in both numerical and graphical formats. Examples illustrating different design and synthesize capabilities are given.