Simplifying Zero Rotations in Cascaded Integrator-Comb Decimators [Tips & Tricks]
David Ernesto Troncoso Romero · IEEE Signal Processing Magazine · 2023
Cascaded integrator-comb (CIC) decimators provide natural aliasing rejection in folding bands. However, improving that rejection requires increasing the number of integrator-comb pairs,N, and this affects the attractive simplicity of the CIC system asNgrows. For a givenN, the worst-case attenuation can still be improved by applying zero rotations. However, state-of-the-art zero-rotation methods introduce coefficients in the CIC filter’s transfer function and therefore complicate the resulting decimation architecture. Here, we show how to rotate zeros in a simple way without these coefficients, such that we only need to add two registers and one adder to the original CIC decimation architecture. Worst-case attenuation improvements can be up to more than 20 dB, depending on the value ofNand the wideness of the folding bands. Other efficient architectures to implement these simplified zero-rotated CIC systems are also presented, and a pruning analysis for these architectures is developed.