The cancellation of interference by sidelobe annihilation

The technique of adaptive array sidelobe annihilation is described. The basic idea is to monitor the output power to see whether it exceeds its nominal level. If it does, interference is assumed to be present. Then one must determine which sidelobe is receiving interference, align a uniformly weighted beam with the boresight of that sidelobe, and subtract a weighted sample of the sidelobe from the array pattern. Because the beamwidth of a uniform beam is greater than that of a sidelobe, some weight adjustment is needed to cancel the interference exactly, starting at the nominal sidelobe level and adjusting the weight down. This adjustment uses a criterion of output power minimization to determine the proper setting of the weight. A functional diagram of the system is presented and experimental results are given. As an example, the cancellation of four jammers over a 2% bandwidth is shown.<>