Lerner-based non-uniform filter-banks and some of their applications

A design process is described which starts with a prototype resonator-based uniform filter-bank, whose bandpass outputs have poor stopband characteristics, and applies the concept of Lerner grouping of adjacent channels to develop a uniform filter-bank with much better bandpass characteristics. For applications requiring the lower frequencies of the input signal to be resolved more accurately than the higher frequencies, the Lerner based uniform filter-bank may be converted to a nonuniform one by applying an allpass transformation; the merit of using such a transformation is that it retains the good magnitude characteristics of the bandpass channels. The main difference between the present design procedure and that of G. Doblinger (1991) is the manner in which the allpass transformation is applied. Further, unlike previous work, the filter-bank designed here has the property that the sum of the bandpass channels is an allpass function. The implementation of the filter-bank is also considered. The primary additional application of the nonuniform channel-bank examined here is frequency-domain adaptive filtering