TABLE OF CONTENTS In previous chapters, various analytical and numerical tools have been presented and applied to simple targets, such as plates and spheres. Most radar targets, with few exceptions (such as weather balloons), are complex geometries with many scattering sources that interact. The interaction between multiple scatterers can cause rapid variations in the RCS as a function of aspect angle. For electrically large targets, the sources can be many wavelengths apart and, therefore, can add constructively and destructively just a fraction of a degree apart.
For example, an aircraft is constantly buffeted by turbulence, which causes its aspect angle, as viewed from the radar, to change. Furthermore, the stressed aircraft frame will deform and flex, changing the separation between scattering sources on the body. This, in turn, causes the aircraft s RCS to fluctuate rapidly as the scattering sources add and cancel as a function of time as well as angle. This apparently random fluctuation, referred to as glint, can result in large range and angle tracking errors.
From a systems point of view, a target can be classified as one of four Swerling types, [*] depending on its scattering statistics1:
S1. The target s return appears to be composed of many independent scattering sources of approximately equal strength. These sources interact at a rate such that the total return is approximately constant for all pulses during a scan of the target but the return is independent from scan to scan.
S2. This type of target has the same...
