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A Physics Based Multi-Resolution Technique for Extraction of Finite Duration Time Responses in ISAR

This paper presents a multi-resolution wavelet analysis technique to mitigate window effect and clutter in radar images. Inverse Synthetic Aperture Radar (ISAR) imaging technique is used to generate the images presented in this paper. Scattering measurements were performed for several target configurations. Utilization of wavelet analysis provides an efficient means to implement gating techniques to remove clutter and isolate other scattering sources to resolve the target. Phase shifts applied to the frequency domain data, prior to wavelet analysis, allow for selection of different instances in time for separation of scattering centers and for visualization of the evolution of scattered fields in time. Results from experimental study are presented in the paper. The analysis was performed with the Daub2 wavelet. It is shown experimentally that the presented multi-resolution technique provides a means to reduce clutter as well as detect targets. It was also demonstrated that the lower resolutions obtained from the wavelet decomposition in k-space correspond to earlier time events and that the higher resolutions correspond to later time events, relative to the reference position. Additionally, an efficient means to remove window effects was demonstrated through removal of the lowest approximation prior to reconstruction of the signal.