Principal components array processing for swath acoustic mapping

The authors propose a new swath mapping sonar design in which the number of concurrent backscatter angles-of-arrival (AOA) is extended beyond the existing limit of one currently afforded by swath bathymetry sidescan (SBS). The AOA estimation method, called “principal components decomposition” (PCD) utilizes an N element sidescan transducer array to estimate, in a total least squares sense over one or more samples, the principal component directions and associated intensities of the received backscatter at each range. PCD affords separation of as many as N-1 concurrent uncorrelated AOAs or N/2 coherent AOAs and unlike conventional beamforming has a resolution limit that is governed by the signal-to-noise ratio rather than the size of the array aperture. This paper presents a synopsis of the theory behind principal components simulated and experimental results for a corner reflector backscattering geometry imaged (mapped) using a six element prototype sonar