EFFICIENT DESIGN OF ADAPTIVE COMPLEX NARROWBAND IIR FILTERS

In this paper a new adaptive complex digital filter structure is proposed. First, a very low sensitivity second-order com-plex bandpass (BP) filter section with independent tuning of the central frequency and the bandwidth (BW) is developed (the low sensitivity of the narrow-band realization is ensur-ing a higher BW-tuning accuracy or better precision in a severe coefficient quantization). Then, a BP/Bandstop (BS) adaptive filter structure is formed around this section, using LMS algorithm to adapt the central frequency. The devel-oped filter circuit is providing a low computational com-plexity and a very fast convergence, and is convenient for cancellation/enhancement of complex sinusoids or narrow-band signals. All theoretical results in the work are verified experimentally