Characterization of near-field scattering using quadratic sensor-angle distributions

We address the problem of characterizing the power attributed to local near-field scattering for the case of a linear equi-spaced array of sensors. The proposed method uses what we have termed the quadratic sensor angle distribution (SAD), previously called the spatial Wigner distribution. This distribution is a characterization of the power at every angle for each sensor in the array. In this distribution near-field sources have different angle for each sensor. The SAD is a joint-variable distribution and a dual in sensor number and angle to Cohen's class of time-frequency distributions. We use a known test source to illuminate the local scatterer distribution we wish to characterize and modify the received array snapshots to remove, via orthogonal projection, the direct propagation path from the test source so as to reveal the less powerful local scatter. An example is provided to demonstrate our technique.