A WISE method for designing IIR filters

The problem of designing optimal digital W filters with frequency responses approximating arbitrarily chosen complex functions is considered. The real -valued coefficients of the filter's transfer function are obtained by nume rical minimization of carefully formulated cost, which is referred here to as the weighted integral of the squared error (WISE) criterion. The WISE cr iterion linearly combines the WLS criterion that is used in the weighted le ast squares approach toward filter design and some time-domain components. The WLS part of WISE enforces quality of the frequency response of the desi gned tilter, while the time-domain part of the WISE criterion restricts the positions of the filter's poles to the interior of an origin-centred circl e with arbitrary radius. This allows one not only to achieve stability of t he filter but also to maintain some safety margins. A great advantage of th e proposed approach is that it does not impose any constraints on the optim ization problem and the optimal filter can be sought using off-the-shelf op timization procedures. The power of the proposed approach is illustrated wi th filter design examples that compare favorably with results published in research literature.