Design of linear-phase digital filters on frequency unequal sample

In this paper, a method and principle for designing linear-phase digital IIR filter based on linear-phase FIR filter is presented. First, a linear-phase digital FIR filter is designed by using unequal sampling theory in the frequency domain. Then in order to satisfy the specialty of the given filter, the amount and frequency positions of these sampling can be simply, directly and easily adjusted while the amount of sampling in time domain does not change. And then a linear-phase digital IIR filter that has the same amplitude with the above-mentioned FIR filter can be obtained by using model reduction based on the impulse-response GRAM matrix.