A beam space adaptive array antenna system utilizing a two-stage Butler matrix configuration is disclosed. The individual elements of one subarray are input to the respective ports of a first-stage Butler matrix and the remaining summed subarray elements are input to a second-stage Butler matrix. The...http://www.google.com.au/patents/US4338605?utm_source=gb-gplus-sharePatent US4338605 - Antenna array with adaptive sidelobe cancellation
