A range and azimuth estimator based on forming the spatial Wigner distribution

We show that for a linear, equally spaced array, wavefront curvature produces a quadratic phase variation across the array for a single arrival frequency from a target within the Fresnel zone of the array. The Wigner distribution for a quadratic phase signal peaks at the instantaneous frequency or, in our case, at the wave number versus array position. By relating this to wavefront curvature, a range estimate is produced.