Adaptive noise cancelling and enhancement of a sinusoid in uncorrelated noise

The response of the adaptive line canceller and enhancer (ALICE) processor to inputs which contain sinusoidal interferences in uncorrelated noise is examined. It is found that under certain conditions the steady-state output power spectrum of ALICE will contain peaks at the frequencies of the interfering sinusoids. In general, the growth time of these peaks is much longer than the ALICE's response time to a signal. However, once the peaks appear at the interference frequencies, their presence may interfere with the detection of other signal peaks in the output power spectrum. Therefore, different methods of eliminating these peaks are examined: increasing the ALE delay, increasing the ANC notch widths, and adding uncorrelated noise to the ALE input. Experimental data that indicate the validity of these analyses are included.