Motion compensation for adaptive horizontal line array processing: A beam domain approach

Abstract

Large aperture horizontal line arrays have small resolution cells and can be used to separate a target signal from an interference signal by array beamforming. High-resolution adaptive array processing can be used to place a null at the interference signal. But these features are significantly degraded by the source motion, which reduces the time period under which the environment can be considered stationary. For adaptive array processing, a large number of data samples are generally required to minimize the variance of the cross-spectral density between the array elements. The penalty of integrating over a large number of samples, when the source and/or interference moves, is the spread of signal and interference energy to many eigenvalues and consequently, the ability to suppress the interference suffers. We adapt a beam domain approach to compensate for the source motion allowing the beam covariance matrix of the signal to be integrated over a large number of data samples without signal energy loss. We employ an equivalent of a rotating coordinate frame to track the signal bearing-change and use the waveguide invariant theory to compensate the signal range-change by frequency shifting. [Work supported by ONR.]