FIR Notch Filter with Rejection Bandwidth Tuning and Sharpening

Two novel design methodologies for the FIR notch filter (NF) are proposed: i) Design with rejection bandwidth (RBW) tuning. ii) Design with narrow RBW. In both methodologies, basic FIR notch filter is evolved from second order IIR notch filter. In the first design, a relationship between pole radius 'r' and RBW is developed for different values of notch frequencies and filter lengths. Such developed relation is used to design an FIR notch filter for the specified RBW, notch frequency and given length. In the second methodology, design of FIR notch filter with highly narrow RBW is suggested. Reduction in the RBW is achieved by choosing high value of 'r' for FIR NF designed from a second order infinite impulse response (IIR) prototype filter and then by using an amplitude change function (ACF): H(z)(2 - H(z)).