Adaptive line enhancement using a second-order IIR filter

A second-order IIR filter is considered as the basic component of an adaptive line enhancer (ALE). As a new feature, the bandwidth of the proposed ALE is adapted simultaneously with the center frequency. This leads to the possibility of combining the convergence speed and accuracy. The adaptation of the filter poles is controlled by a sign algorithm. The step sizes are chosen such that transients caused by the retuning of the filter are ensured to remain much smaller in amplitude than the response of the filter to the input signal. When the input signal consists of a sinusoid corrupted by wideband noise, an accurate frequency parameter estimate can be obtained with the algorithm given in the paper