Closed-form approximation of linear phase IIR digital filters with guaranteed stability

We develop a closed-form approximation algorithm for de signing IIR digital filters with linear phase and guaranteed stability. In this algorithm, the stopband and passband edge frequency can be specified in the frequency domain and the filter coefficients can be easily obtained for approximating the given frequency response. Additionally, there is a property that the maximum of absolute values of all poles can be con trolled, so we can avoid the risk that the designed filters under finite word-length effects become unstable. Finally, a numerical example is given to illustrate the utility of the proposed method.