Design of IIR-like filter blocks in cascade for generating narrow transition-band linear-phase FIR filters

A class of filter structures requiring small number of components is introduced for implementing narrow transition-band linear-phase FIR filters. The impulse response of this class of filters is a truncated and shifted version of that of a stable IIR filter, cascaded with its unstable counterpart. The truncation is performed using a feed-forward term, which provides pole-zero cancellation(s). Both filters are implemented as a parallel connection of several branches, in which each branch generates a truncated response corresponding to a real single pole or a complex conjugate pole pair. The implementation uses the principle of switching and resetting between two identical copies of the same IIR filters, to stabilize the pole-zero cancellations and to prevent the quantization error from growing excessively.