Compensation method for the CIC filter in digital down converter

CIC filter, for its simple structure without using multipliers, is widely used in digital down converter to achieve efficient digital filtering. However, it has an inherent pass band magnitude droop. Compensation filter is required in a bandwidth requirements system. A number of different methods which have been proposed can only compensate a narrow pass band segment of the CIC filter. In this paper, a method with the structure of polyphase decimation FIR filter is proposed to achieve wide broadband compensation of the CIC filter and sampling rate conversion.