The Research Of Clutter Suppression Using A Priori Information

When radar detects and perceives the surroundings, the strongly clutter from the ground and sea surface will have undesirable effect on radar system. How to do clutter suppression effectively is an important research direction, especially in the complex geographical environment. Space-time adaptive processing(STAP) techniques, which have been developing over the last thirty years, have made great achivements in theory, However, there are still some problems to be sloved in practice. Generally, when the airborne radar looks downwards, the clutter circumstances are inhomogeneous, resulting in insufficient independent and identically distributed secondary data,which may increase the estimation error of covariance matrix, and decrease the system performance of radar system. Along with the rise and development of cognitive radar, a new intelligent clutter suppression method based on priori information has got more and more attention. People focus on all kinds of transmit waveform and beampattern design methods.In this thesis, the properties of two-dimensional space-time clutter spectrum and airborne radar echo model are introduced in the first place. Through the analysis, full rank STAP exhibits excellent performance, but the computation load and the need for adequate homogeneous training data limit its application.The reduced-dimension STAP can overcome these problems to a certain extent. Then we introduce several common reduced-dimension STAP methods in detail, and make comparisons on the capable of clutter suppression. In the second place, on the scenario of heterogeneous airborne clutter, a kind of transmit beampattern design method with priori information about clutter suppression is introduced. Compared with the traditional model of phased-array in pulse-dopplor treatment, in azimuth non-uniform and distance dimensions of inhomogeneous clutter scenes, the optimization design method will form a notch in the doppler channel of strong clutter at all distance unit, this reflects the capability of clutter suppression at sidelobe location. Finally, the joint optimization method on the constant modulus of waveform and receiving filter is proposed in complex geographical environment, and the response of clutter information has already known. This method uses alternating iterative optimization and convex optimization method, by designing a set of waveform and corresponding mismatched filter to suppress the clutter of mainlobe. Also, the clutter intensity and the peak to average ratio of radar echo will drop, this will be of great importance to the subsequent detecting and tracking process.