STUDY OF THE NULL DIRECTIONS ON THE PERFORMANCE OF DIFFERENTIAL BEAMFORMERS

Null directions are important parameters for differential beamformers, which play an important role on the beamforming performance. In this paper, we investigate the performance of differential beamformers as a function of the null directions. We first derive the directivity factor (DF) as an explicit function of null and show that the DF decreases to 0 if any null approaches to the desired look direction. We then validate the theoretical analysis through simulations using the beampattern, DF and signal-to-interference gain as the performance measures. The results show that: 1) the performance of a differential beamformer degrades significantly if there is any null close to the desired look direction; 2) with a fixed null direction, increasing the order of the differential beamformer can help improve performance.