A sine-cosine-like CIC filter

The traditional CIC filter does not require any multiplier or coefficient storages, therefore it’s used widely in various sampling rate conversion system. However, the traditional CIC filter has high pass band distortion and low stop band attenuation, and its integrator is operated at high rate, all of these greatly limit its applications in the sampling rate conversion system that requires higher performance. All kinds of CIC filters, such as sharpened CIC filter, ISOP-CIC filter, the CIC-Cosine filter and so on, were presented later. But they either only improved the pass band characteristics, or only improved the stop band characteristics, or their integrators were operated at high rate. Based on analysis and comparison of the frequency characteristics among the traditional CIC filter, sharpened CIC filter, ISOP-CIC and CIC-Cosine filter, a cosine-sine-like CIC filter which consists of a cosine-like pre-filter, a sine-like pre-filter and multi-stage cascade of the traditional CIC filter is proposed. The sine-like pre-filter presented can reduces the pass band distortion of the whole CIC filter, and the cosine-like pre-filter can increases the stop band attenuation. Simulation results show that the proposed cosine-sine-like CIC filter provides lower pass band distortion and higher stop band attenuation, contrast with the traditional CIC filter, ISOP-CIC filter and CIC-Cosine filter. At the same time, the two pre-filters presented both run at low rate, multistage CIC filter can also be moved to low rate, by the use of polyphase decomposition.