Mainbeam nulling with adaptive array interferometry

The authors consider the main beam patterns produced by an adaptive array consisting of two distinct antenna arrays that may be separated by many wavelengths. This type of adaptive array produces patterns that typically have very narrow nulls in the direction of the interference and preserve a main beam shape except for undesired grating nulls within the main beam pattern. These grating nulls can be filled in by averaging the patterns achieved at several operating frequencies. The authors discuss the adapted patterns and SINR (signal-to-interference-plus-noise ratio) performance for several types of these interferometric adaptive arrays. The effects of auxiliary element location and signal geometry are considered. Experiments results from an interferometric sidelobe canceler are presented. It is observed that, if low sidelobe quiescent patterns are desired, a sidelobe canceller array does better than a fully adaptive array with the same quiescent pattern. In these cases the adapted patterns are dominated by the auxiliary array