A design technique for variable digital filters

In some applications the frequency characteristics of a filter may be required to change during the course of signal processing. This requirement can be satisfied by filters with coefficients that are directly computable from the specified spectral parameters. Such filters are referred to as variable filters. A design technique for variable filters is proposed. The filter coefficients are expressed as analytical functions of the frequency specifications by using a curve-fitting technique. Several examples are presented to illustrate the method.<>