Improved interference cancellation in synthesis array radio astronomy using auxiliary antennas

Spatial filtering and subspace projection methods have been proposed for removing interference signals at radio astronomy (RA) imaging arrays. Given the fact that RA signal levels are usually below noise levels, and since high gain antennas significantly reduce the interference to noise level at antenna feeds, it is often difficult to form the accurate interference signal parameter estimates. By adding a few (1-3) low gain "auxiliary" antennas to an imaging array, it is possible to overcome this problem. Using low cost auxiliaries with an existing array can improve interference rejection by tens of decibels. New extensions to subspace projection spatial filtering methods are presented, along with simulated results for performance comparison.