Passive Imaging of Moving Targets Using Distributed Apertures in Multiple-Scattering Environments

We present a novel passive image formation method for moving targets using distributed apertures capable of exploiting information about multiple-scattering in the environment. We assume that the environment is illuminated by non-cooperative transmitters of opportunity with unknown location and unknown transmitted waveforms. We develop a passive measurement model that relates the scattered field from moving targets at a given receiver to the scattered field at other receivers. We formulate the passive imaging problem as a generalized likelihood ratio test for a hypothetical target located at an unknown position, moving with an unknown velocity. We design a linear discriminant functional by maximizing the Signal-to-Noise Ratio (SNR) of the test-statistic, and use the resulting position-and velocity-resolved test-statistic to form the image. Our imaging method can determine the two-or three-dimensional velocity vector as well as the two-or three-dimensional position vector of a moving target without the knowledge of transmitter locations and transmitted waveforms. We present numerical experiments to demonstrate the performance of our passive imaging method operating in multiple-scattering environments. The results show that the point spread function of the reconstructed images improves when the information about multiple scattering is exploited.