Overview

In this chapter we discuss two specific problems of space-time adaptive processing for SAR and ISAR.

The first problem is strongly related to clutter suppression as has been treated in previous chapters. The question to be answered is how far inverse synthetic aperture (ISAR) imaging of moving targets by a moving phased array radar is degraded by space-time clutter filtering. ISAR techniques exploit the target motion rather than the radar platform motion for imaging of moving targets. Details of the principles of ISAR can be found in Wehner [541, pp. 341].

Since space-time filtering techniques include the time dimension and ISAR is a temporal (pulse-to-pulse) compression technique some effect of clutter filtering on the ISAR resolution can be expected. We consider here space- time filtering. The effect of space- frequency clutter rejection techniques (see Section 9.5) will be similar. Since it is closer to our previous considerations on space-time processing we start with the ISAR problem. It should be noted that we will treat here the more complex problem of space-time clutter suppression for ISAR with a moving radar platform. Similar results can be obtained for a stationary radar with temporal clutter filtering only. Even conventional processing (applying a temporal clutter rejection filter to SAR data, see for instance Medlin [344, 345]) will cause some distortions of the ISAR chirp due to a moving target.

One of the earliest publications on ISAR was by Wirth ^[1] [550]. The author used data...