Multistage, Multirate FIR Filter Structures for Narrow Transition-Band Filters

Abtrac t This paper presents an FIR fllter system capable of implementing virtually any practical lowpass and highpass filter with as little as 60-60 multiplications per sample. The method b based on multirate techniques and complementary Alters. We first give a brief presentation of the principle and the necessary building blocks. Then, practical design methods for optimitation are presented together with design examples and plots of the multiplication rates. Finally, aliasing and flnite wordlength effecb are discussed. The resulting system, while having a remarkably low arithmetic complexity, will usually require somewhat more memory than a conventional optimum direct-form filter and a slight increaee in the internal signal representations.