Guest Editorial: Low-Power Digital Filter Design Techniques and Their Applications

Welcome to this Special Issue on Low-Power Digital Filter Design Techniques and Their Applications. Digital filters are essential elements of many signal processing systems and everyday electronics such as radios, cell phones, and biomedical devices. With the ever-increasing popularity of portable devices in communication, medical, and audio/video systems, the computational efficiency and power consumption of digital filters have become increasingly a matter of concern, as digital filters usually involve a large number of arithmetic operations, especially for the finite impulse response (FIR) filters. While FIR filters do have merits in stability, linear phase property, and low coefficient sensitivity, they consume more power than their infinite impulse response (IIR) equivalents in general. There has been consistent effort to develop low-power techniques for FIR filters in the past half century, such as multirate filtering, subfilter approaches, and multiplierless filtering. In multirate filtering, arithmetic units are shifted to the lower frequency end, resulting in reduced power at low operation frequencies. In subfilter approaches, filters are connected in series and/or parallel to form a network, where the frequency responses of different frequency intervals are taken care of by different filters or filter pairs. The overall number of non-trivial coefficients can be significantly reduced by cleverly arranging the subfilters. A very successful subfilter structure is the frequency-response masking (FRM) structure, which was first proposed in 1986 by Y.C. Lim. In 1979 Lim pioneered multiplierless filter-