Non-circularity coefficient estimation of the SOI for narrowband widely linear beamforming

In widely linear beamforming, the second-order non-circularity property exhibited by the signal-of-interest (SOI) can be exploited to improve interference and noise suppression. Assuming known SOI steering vector and spatially white noise, several algebraic schemes for estimating the SOI non-circularity coefficient are proposed in the context of narrowband widely linear beamforming without training/reference signal. These new estimators are based on signal purification, pseudoinverse, oblique projection, and pre-processed subspace separation. Simulation results are included to illustrate the performances of the proposed methods.