Recent progress in the application of wavelets in surveillance systems

Abstract

We briefly discuss two approaches for enhancing the resolution enhancement of range-Doppler images (including synthetic aperture radar and inverse synthetic aperture radar images). The first approach can be used in conjunction with current radar systems that use a fixed narrowband waveform to acquire target data. It measures Doppler shifts more accurately than the traditional fast Fourier transform based techniques. It performs well in low signal-to-clutter regimes regardless of the statistical structure of the clutter. The second technique assumes that the radar can transmit different waveforms that are matched to the imaging task under consideration. It is based on the fact that the most accurate reconstruction of a range-Doppler target density function from <i>N</i> waveforms and their echoes is obtained by transmitting the singular functions corresponding to the <i>N</i> largest singular values of two kernels derived from the target density. We discuss two strategies for selecting the radar waveforms. The first strategy uses fixed waveforms that act as approximate singular functions for the kernels corresponding to wide classes of target densities. The second strategy adaptively selects the transmitted waveforms by solving a simultaneous target classification and image reconstruction problem.