Subfilter approach for designing efficient FIR filters

Recently, several special filter structures, together with the design methods, have been proposed for reducing the cost of implementation of FIR (finite-impulse response) filters. The authors review some of the techniques based on the use of subfilters as basic building blocks. There are basically two different subfilter approaches, the first one using different subfilters and the second one using identical subfilters. The authors concentrate on the design of lowpass filters, even though most methods considered can be applied equally well to the design of other types of filters