Abstract

A solution based on the application of the ISAR processing to compensate the unknown part of the relative motion between radar and non-cooperative moving target is proposed. The functional block diagram is shown in Figure 9.1 and it is composed of the following main steps:

Target Detection. Every target to be refocused must be detected within the SAR image first. This is a crucial step because the unknown target motion leads to dispersion of the useful target energy over a wide region. Detection is critical when dealing with ground target because of strong clutter.

Target sub-image selection. Once detected, every target must be cropped and separated from every contribution due to clutter and other targets. In this way, a number of sub-images equal to the number of detected targets is obtained.

Sub-image inversion. Since the ISAR processing takes raw data as input, an inversion mapping from the target image to the target raw data is mandatory. It is worth highlighting that raw data obtained from the whole SAR image is not a suitable input for the ISAR processing because it usually contains the returns from several moving targets, each one with its own motion. ISAR processing must be applied to a single target raw data at each time.

ISAR processing. It performs motion compensation and image formation.