FIR DIGITAL-FILTER DESIGN WITH VARIABLE PARAMETER WINDOW FAMILIES

It is well known that the design of nonrecursive digital filters of the lowpass, symmetric bandpass and highpass types using the window function approach is simple and quite easy to implement. It has already been shown that the Io-sinh family of window functions gives designers flexibility because of its adjustable parameter. In this paper, two other well-known window function families, namely the I1-cosh and raised-cosine types, which have variable parameters to control the ripple, are considered. Expressions are derived for filter order in terms of ripple magnitude and transition bandwidth. The performance of these two families are compared with the modified zeroth-order Bessel (Io-sinh) family and the results in the time and frequency domains are presented.