Options
2001
Conference Paper
Titel
Space-time Adaptive FIR Filtering with Staggered PRI
Abstract
Space-time adaptive processing (STAP) has been recognized as an indispensable tool for detection of moving targets by air- or space borne MIT radar. Future military observation systems will include combined Synthetic Aperture Radar (SAR) and ground moving target indication (GMTI) modes. GMTI techniques are in general based on STAP techniques. One of the major issues of implementing STAP techniques is the complexity of STAP architectures. A great deal of papers have been published on subspace techniques which reduce the amount of operations required for adaption, filter calculation and filtering. Some of these techniques are based on rank reduction of the space-time covariance matrix, others on the principle of order reduction. Space-time FIR filters belong to the class of order reduced processors. They have been proven to achieve near optimum clutter cancellation performance at dramatically reduced number of operations [1, 2, 3]. Real-time processing capability has been proven by implementation on a Mercury multi-processor system. Besides a few disadvantages concerning the implementation the choice of a staggered PRI code offers some significant advantages: 1. Unambiguous estimation of the target Doppler; 2. Elimination of blind velocities; 3. Reduction of the threat posed by spot jammers. In this paper the effect of staggered PRI on STAP FIR filtering is discussed. It is shown that 1.the optimum fully adaptive processor based of staggered PRI works almost perfectly; 2. a FIR filter with constant coefficients suffers considerable losses compared with operation at constant PRI; 3. A reasonable clutter rejection performance is achieved be readapting the filter at each PRI. As far as implementation is concerned readapting the STAP FIR filter at each PRI does not pose a significant problem since the number of filter coefficients can be chosen very small. Therefore, the number of training samples and hence the number of operations required for adaption is small too so that the filter coefficient can easily be calculated using the data received during one PRI. In the paper a comparison of the performance of the STAP FIR filter using uniform or staggered PRI made. It comes out that staggering leads to losses in signal detection performance of a few dB.