Novel two-stage comb filter for multiple-of-three decimation factors

This paper presents a novel two-stage comb filter for multiple-of-three decimation factors. The first stage is a comb filter decimated by one third of the overall decimation factor, while the second stage is a comb decimated by three. The expanded cosine filters are cascaded with a comb filter at the first stage to improve aliasing rejection in the third folding band. The efficient structures are also presented. The method is illustrated with one example. The benefits of the method are shown in comparisons with some methods proposed in literature.