The technique of non-equiripple approximation for filter characteristics is presented.In this technique the characteristic function is composed of the rational function constructed by Chebyshev polynomial and coefficients related to frequency. Thus the attenuation characteristics close to thos of elliptic filter for the same order are obtained. The computing results show that the technique of non-equiripple approximation has advantages over Chebyshev filter and inverse Chebyshevfilter. The design procedure is not only clear in theory

but also simple and easy to complete computer program. The approximation method based on non-equiripple is an intermediary between equiripple approximation and maximally flat approximation. It is quite useful for filter design.