Simplified realization of cascaded adaptive notch filters using complex coefficients

In this paper, we present a new structure for a complex adaptive IIR notch filter which is useful for the rejection of narrow-band interference from broad-band signals in QPSK communication systems. The proposed structure is based on the direct form first-order complex notch filter using gradient-based algorithm. By using the proposed first-order section, a new cascaded structure for complex adaptive notch filter has been shown. The results of computer simulation are shown which confirm the theoretical prediction.