A Complexity Reduction Approach for FIR Notch Filter Design

A structure for reducing the complexity of FIR digital notch filter is proposed. The structure is composed of two sub-filters and a delay branch. First, an interpolated single point pass prototype filter and a masking filter are cascaded. Then, the cascaded sub-filters are paralleled with the delay network. Numerical experiments show that multipliers and adders used in notch filter can be reduced about 10%～90% compared to direct design, and the saving percentage is related to filter’s transition band width, while the notch frequency is indifferent to it. Even more multipliers and adders can be saved for notch filter with narrower transition band width. The only shortcoming of the proposed approach is that some additional delays are required. The formulae for calculating subfilters’ parameters are also proposed.