A New Adaptive Blocking Matrix with Exact Fir Structure for Robust Generalized Sidelobe Canceller

To improve the robustness of the generalized sidelobe canceller (GSC) against steering error and inevitable misdetection of adaptation mode control (AMC) in real applications, the conventional adaptive blocking matrix (ABM) consists of coefficient-constrained adaptive filters (CCAFs) which use the output of delay-and-sum fixed beamformer (FBF) as input, in order to limit the tracking range of the ABM. Since the output of FBF is a FIR-like response for directional signal, the attempt of inverse filtering with a FIR-based CCAF in the conventional ABM will result in irregular spread and oscillation of coefficients. As results, the actual tracking range varies with the signal frequency, and the rejection of low frequency interference will be deteriorated in the case of misdetection of AMC. This paper proposes a new ABM with exact FIR structure, in which the output of FBF is used as desired signal, thus the coefficients oscillation caused by inverse filtering is eliminated. Coherent tracking range can be achieved across full frequency band by simply constraining the pulse width of the ABM filter response. Experiment in real environment shows that the loss of interference rejection caused by misdetection of AMC is reduced significantly.