Complex adaptive IIR notch filter algorithm and its applications

In this paper, conventional real coefficient adaptive notch filters (ANF´s) are extended to complex coefficient ones. This complex adaptive notch filter is implemented as a constrained IIR filter using a complex Gauss-Newton type algorithm to adjust its coefficients. When the ANF algorithm is applied to estimate the frequencies of sinusoids embedded in white noise. The results show that this algorithm has fast convergence, small bias, and achieves the Cramer-Rao bound. Furthermore, this ANF algorithm is used to estimate the parameters of multiple chirp signals. Simulation results also demonstrate very good performance. Finally, when this ANF algorithm is used to suppress narrowband interference in QPSK spread spectrum communication systems, the analytic result reveals that its signal-to-noise ratio improvement factor is grater than the factor of conventional one-sided prediction filter