On the use of beamforming for estimation of spatially distributed signals

In wireless communications, spatially distributed signals originate from local scattering around the transmitter. Spatially distributed signals cause conventional high-resolution methods to show degradation in performance, since the underlying data model is of full rank theoretically. In this paper, a relationship between the distribution of the spatial spread and the power azimuth spectrum is derived. Using this relationship, two simple and robust estimators based on the conventional beamformer and Capon´s beamformer for estimation of the nominal direction and spatial spread are found. The proposed estimators show very good performance in numerical examples.