Improving Passband in Cosine-Based CIC Decimation Filter with Improved Worst-Case Aliasing Attenuation

This paper presents the design of a compensator for the cosine-based CIC (Cascade-Integrator-Comb) decimation filter proposed in the literature for even decimation factors. This decimation filter improves the worst-case aliasing rejection in the first folding band. Additionally, the aliasing rejection is increased in all odd folding bands using a modified cosine filter. However, as a result, the passband droop is increased compared with the CIC filter. We aimed here to design a compensator to decrease passband droop. We consider the wideband case. The magnitude characteristic of the compensator is composed of two sinusoidal functions. The design parameters are the amplitudes of sinusoidals and the parameter of the modified cosine filter. The designs with multipliers and without multipliers are presented and illustrated with examples. For orders of CIC filter less than six, the maximum passband deviation of the compensated filter is less than 0.05 dB. The complexity of the overall design is expressed in the number of APOS (Adders per Output Sample). The proposed design is compared with the compensated decimation filters from the literature.