Speckle Statistics in Adaptive Beamforming

Abstract

We have examined the statistics of the speckle patterns in images formed using delay-and-sum and min- imum variance beamforming. We show how the estimate of the spatial covariance matrix used in the latter beam- former affects the speckle patterns. By using purely spatial averaging in the estimate the speckle statistics are quite different from delay-and-sum: Areas that are apparently homogeneous in delay-and-sum images appear as a collec- tion of point scatterers in the minimum variance images, reducing the overall brightness of the speckle. We show that temporal averaging reduces this effect without compromising the improved spatial resolution offered by the minimum variance beamformer. Results from both simulations and experimental RF data are shown.