Alternative approaches to generalized sidelobe canceler beamformer
* Presenting author
Abstract:
The generalized sidelobe canceller (GSC) decomposes the beamforming into two paths: The upper path is to preserve the desired signal, the lower path is to suppress the desired signal. From beampattern perspective, we propose alternative approaches to the GSC, the new algorithms mainly modify in the lower path, that is, instead of using the blocking matrix to suppress the desired signal, we design a beamformer that contains the nulls at the look direction and some other directions. We claim that the beamforming with a null at look direction performs a similar function to the blocking matrix. Moreover, the GSC subtracts two beampatterns to suppress the side-lobes, this amplifies noise when the sidelobes of the upper path's beampattern are not identical to the lower path's beampattern, especially at the null positions of the upper path's beampattern. To tackle this issue, we insert those nulls to the lower path's beampattern to increase the similarity of the beampatterns at two paths. By doing so, we propose two variants of the GSC, one is the fixed beamforming where the adaptive filter in the lower path of the GSC is removed and the other is the adaptive beamforming where only one adaptive filter is used.