11.1 Introduction

The mission of a surveillance radar is the detection of moving targets, either airborne or ground-based, known as moving target indication (MTI). Traditionally, MTI radars have been implemented with a pulsed waveform using antenna reflectors or phased arrays with a limited number of spatial channels. Future systems, however, will most likely be implemented with antenna arrays with a large number of spatial channels to greatly enhance detection performance, especially in the presence of interference, through adaptive processing. The spatial channels formed from the antenna array, either beams or subarrays, provide angle measurements, and pulses are used to extract velocity information on potential targets. For each pulse, the radar returns are digitally sampled in time where each sample corresponds to a range or distance from the radar. The entire collection of spatial, pulse and range samples makes up a three-dimensional datacube.

The key challenge to an MTI system is the suppression of interference, either due to other transmitted signals, such as jamming, or from the ground reflections of the transmitted radar signal, known as clutter. The fundamental problem that ground clutter presents is that, despite the fact that it is not physically moving, it has a nonzero Doppler frequency due to the platform motion of the MTI radar. As a result, the detection of moving targets that share the same Doppler with ground clutter is severely impaired without adaptive clutter mitigation. The physical characteristic that can be exploited, however, is the fact that ground clutter with...