Low-power decimator design using approximated linear-phase N-band IIR filter

This correspondence presents a new design of a low-power decimation filter, which consists of a poly-phase finite-impulse-response (FIR)-4 comb filter, an approximate linear-phase one-third-band infinite-impulse-response (IIR) filter, and a half-band FIR filter. A poly-phase FIR-4 comb filter architecture was designed, which consumes 75% less power than the recursive comb filter architecture. New general equations were derived for the design of 1/N-band IIR filters, and these equations were used to design a novel approximate linear-phase one-third-band IIR filter. The decimation filter is designed using Simulink and DSP Blockset, and Matlab simulations are performed to verify the phase linearity and magnitude response of the designed filter. The group delay for the passband region of one-third-band IIR filter has a negligible error of 0.009%. The resulting decimation filter has 60% less hardware and consumes 67% less power than the comb-FIR-FIR decimation filter.