Alternative Data Paths for the Cascaded Integrator-Comb Decimator [Tips & Tricks

Abstract

Alternative data paths for the cascaded integrator-comb (CIC) decimator are presented that can be derived upon applying one or two modifications. In the first modification, the integrator-comb pair that surrounds the downsampling register is replaced by a simpler Integrate-and-Dump (ID) block that performs the same decimation task. The resulting data path is referred to as CIC-ID. In the second modification, the remaining comb filters are replaced by a timemultiplexed comb, and the resulting data path is referred to as CIC-ID-TMUX. Compared with a classic N-stage CIC, CIC-ID saves one arithmetic unit and one register, whereas CIC-ID-TMUX uses the same number of registers but trades (N - 1) arithmetic units for a simpler two-to-one multiplexer. Both CIC-ID and CIC-ID-TMUX perform slightly fewer arithmetic operations per output sample because of the absence of the comb filter absorbed by the ID block. Pruning formulas for both architectures are presented along with implementation details.