Performance Analysis Of The Methods Of Space-time Adaptive Processing

Clutter suppression is critical to airborne early warning surveillance sensors. In addition to the conventional techniques such as low sidelobe antennas and displaced phased center antenna(DPCA),there has been great interest in space-time adaptive processing(STAP) because it can suppress clutter effectively and improve the detection performance of airborne phased array radar evidently. The research on STAP began in 1973 and has been performed for more than 20 years. Because of the computation load and the implementation complexity of full rank STAP are too great to be accepted and it is really very difficult to obtain enough samples to estimate the covariance matrix. The focus of successive research is concentrated on the reduced-rank algorithms and many reduced-rank methods have been proposed.In 1996, H.Wang et.al. proposed a new reduced-rank STAP which has only two spatial degrees-of-freedom(DOF). They call itΣ△- STAP because the two channels are the sum and difference beams of the antenna. Their interest inΣ△- STAP stemmed from the fact that antenna engineers have excelled in the design of high performance sum and difference beam either for phased array or for reflector antenna. Their research shows theΣ△- STAP can provide good clutter-suppression performance in some cases and has many advantages. But it also has many limitations and in some cases its performance is not satisfying.In the paper, we describe the principles of the fixed reduced-rank methods firstly. Then several Doppler-domain reduced-rank methods are discussed including aΣ△- STAP approach which is calledΣ? - EFA andΣ△- WARD. Analysis and simulations are given showing theΣ? - EFA andΣ△- WARD has satisfying clutter suppressing performance and improvement factor in ideal system condition. But in actual condition the performance ofΣ? - EFA andΣ△- WARD will degrade seriously. So in the next Chapter some non-ideal conditions are considered. They are the property of sum and difference beams, the errors of the elements and channels and different pulse repeating frequency(PRF). Finally simulation results validate the effectiveness of the methods presented in this dissertation.