Wideband adaptive arrays based on the coherent signal-subspace transformation

This paper presents a family of adaptive arrays which are based on approximations of the Coherent Signal-Subspace (CSS) processing method [1]. This approach requires a preliminary estimation of the directions of arrival of the signals. The array structure includes a frequency-dependent transformation stage followed by a narrowband constrained nulling procedure. If the exact CSS transformation is used, it is shown that the steering and nulling bandwidth of the array becomes infinite. Realizable approximations to the exact transformation are then presented.