Nonrecursive digital filter design using the ultraspherical window

A method for the design of nonrecursive digital filters using the ultraspherical window is proposed. The method is based on empirical formulas for the filter length and the independent parameters of the window that would achieve prescribed specifications in lowpass filters. Extensive experimental results show that the ultraspherical window yields lower order filters relative to designs obtained with the Kaiser and Dolph-Chebyshev windows. Alternatively, for the same filter order, the new method results in reduced passband ripple and increased stopband attenuation.