Sidelobe level degradation in adaptive sidelobe cancellers with element reuse

The authors examine the performance of sidelobe canceller (SLC) arrays in which both the main antenna and the auxiliary antennas are formed from combinations of the same elements in a large phased array. This sharing of elements between mainbeam and auxiliary signals is referred to as element reuse. It is shown that whenever the number of adaptive degrees of freedom exceeds the number needed to suppress the interference, the noise correlation may lead to large weight magnitudes and large sidelobe level increases. This effect is undesirable in radar applications where the mainbeam pattern is designed for low sidelobes and retention of these low sidelobes is essential to avoid clutter degradation. It is shown how this problem may be overcome by forming the auxiliary signals from element combinations in such a way that an orthogonality condition between the auxiliary and mainbeam combiner weights is satisfied.<>