New method of FIR comb filtering

Comb filters are used in several applications. For example, the CIC filter is often used in multi-rate signal processing. IIR comb filters are used to notch out harmonic interference. The FFT can also be used as a comb filter, but because of the computational complexity and other limitations, it is not usually used for this application. A new formulation of the FFT comb filtering is presented that eliminates all limitations of the FFT method and provides advantages over the IIR comb filter. In this paper, it is mathematically proven that the FFT comb filter can be transformed to a computationally efficient equivalent structure. It is further shown that this structure can also be implemented as a simple FIR filter.