5.1 Introduction

So far the high-resolution radar techniques used for target recognition described in the book have been associated with spatial attributes of the target. The high-resolution range profiling, the SAR and ISAR techniques all provide high-range resolution signatures of the target from reflections of the radar signal associated with scattering occurring from a particular area of the target. These methods have been based on the physical size and shape of the target remaining constant during the radar integration period, with SAR and ISAR being reliant on changes in aspect angle for a rigid target. The signal processing methods used to generate the SAR and ISAR images have assumed that the scatterer retains its relative position on the target over the period of the radar measurement. No moving parts of the target have been addressed and it has been assumed that range profiles and two-dimensional synthesised images have been derived from a target both with a stable geometry and stable scattering characteristics. Within this chapter a totally different approach is taken. The physically stable parts of the target are not used and it is the moving parts of the target that are utilised in the target recognition process. The moving parts of most interest are associated with the propulsion systems of the targets, particularly for aircraft. Any mechanical parts of the aircraft which are moving or rotating relative to the main body of the aircraft, and are illuminated by the radar signal, are potential candidates for providing attributes for target...