Blind equalization of phase aberrations in coherent imaging: medical ultrasound and SAR

This work introduces a novel auto-focusing phase aberration correction algorithm for coherent imaging systems such as medical ultrasound and synthetic aperture radar (SAR). The algorithm follows directly from the analytical expressions obtained from a detailed theoretical analysis of the scattering of wave packets in a random scattering medium consisting of many scatterers in each resolution cell. The algorithm selects the resolution cell in a range-azimuth region with the smallest ratio of the variance of the focused channel/element amplitudes to the mean square of the focused channel amplitudes. The aberrant phase can be estimated directly from this selected cell using well known phase gradient techniques. Monte Carlo simulations are shown to exhibit excellent algorithmic performance