Broadband source tracking using adaptive directional filter with maximally flat responses at null directions

A new algorithm for the tracking of broadband sources in linear arrays employing tapped delay line processing is presented and investigated. Using this technique, each broadband source is individually tracked in a time-multiplexed manner by steering a broadband null formed from the use of a tapped delay line filter whose weights are constrained to have a maximally flat frequency response at the nulling direction. To ensure that the other nulls are not changed while a particular null is being adjusted, a beamformer is employed to preprocess the element signals before adaptive processing. Since the new algorithm updates only one tapped delay line filter at any instant, the overall implementation complexity of the proposed algorithm is comparable with using the LMS algorithm directly on a broadband array. However, unlike the latter algorithm, the convergence behavior of the new algorithm is significantly faster and is almost independent of the external noise environment.