Space-based Radar Clutter Modeling And Simulation

Space-Based Radar (SBR) is a radar system using satellites as a platform for long-range target detection and tracking. Because of its all-weather working, space exploration, early warning a long time, anti-destroy ability, freedom from restrictions on airspace and curvature of the Earth, etc., SBR has become an important research topic in recent years. Air moving target indicator (AMTI) is one of the important applications and clutter suppression is the key to moving target detection technology.In this dissertation, the two-dimensional space-time clutter characteristics of the ground clutters are analyzed in detail, in order to further study clutter suppression and moving target detection. The main contents are as follows:1. The six coordinate systems in SBR's geometry scene, as well as their mutual transformational relation are analyzed. Then, the mathematical model which establishes the geometrical relationship between SBR and clutter scatterers is set up. According to the model, the relationships between distances and angles are presented. Finally, the Azimuth-Doppler trajectories are provided to examine the model. The model is valuable for research of clutter suppression in SBR radar systems and may be the foundation of studying ground clutter characteristics and modeling.2. The statistical properties and the power spectral characteristics of radar clutter are introduced, and those unique characteristics of radar clutter, including effects of range ambiguity, doppler ambiguity and the Earth's rotation on ground clutter are analyzed in detail.3. By setting up the space-time two-dimensional model of radar ground clutter, characterizing spectrum and power spectrum that are derived from the clutter covariance matrix are studied in detail. Given radar parameters, the clutter covariance matrix, eigenvalues and clutter power are obtained, and the simulation results of Angle-Doppler spectrum, Angle-Doppler trajectory, Range-Doppler spectrum and clutter characterizing spectrum, are given by using Matlab. Through deep analysis of these simulation results, we can conclude that the effects of the Earth's rotation on radar clutter are that the clutter Degree of Freedom(DOF) increases with the crab angle and the Angle-Doppler trace changes from a straight line into a curve. The characters of high position and faraway distance need low PRF, on the other hand, the fast moving target indicator requires high PRF. In fact, the higher value of PRF, the more serious is the Range ambiguity. On the contrary, the lower value of PRF, the more serious clutter is the Doppler ambiguity.It is worth noting that different main beam width will have an impact on the clutter Range ambiguity in the case of a specific PRF and other parameters. For example, the value of the main beam width is so large that a certain degree of Range ambiguity will appear. Finally, those difficulties and challenges to clutter suppression resulted from Range ambiguity and Doppler ambiguity are analyzed.