Study On Clutter Simulation And Suppression Method Based On Knowledge Aided For Airborne Radar

The ground clutter return power is usually very strong when the airborne radar operates at a look-down mode. And in complex terrain environment, the clutter shows a significant heterogeneity, which makes it difficult for airborne radar to detect moving targets. Consequently, the analysis of clutter characteristic and the research of clutter suppression technique are necessary. However, because of the long time and the high costs it takes to acquire radar measured data, utilizing the computer simulation method to simulate clutter data is indispensable.Space time adaptive processing(STAP) is a two-dimensional adaptive filter that combines spatial domain and time domain information to realize clutter suppression. It can effectively suppress the clutter and simultaneously guarantee the coherent processing gain for the interested target. Therefore, space time adaptive processing becomes a key technique for clutter suppression in airborne radar. Theoretically, in order to get an optimal STAP performance, the number of independent identical distributed training samples for estimation of clutter characteristic should be larger than two times of system degree of freedom. However, the heterogeneity of real clutter makes training samples insufficient and the performance of STAP will be significantly degraded.This dissertation focuses on the study of heterogeneous clutter simulation and suppression methods. The main work can be summarized as follows:Firstly, this dissertation analyzes the airborne radar clutter signal mathematical model. Then it outlines the basic principles of space time adaptive processing. And several common reduced-dimension space time adaptive processing are simulated and analyzed.Secondly, focusing on heterogeneous clutter simulation method, this dissertation explores a heterogeneous clutter simulation method based on digital elevation and land cover. A series of problem are solved including coordinate transformation, shadowing, calculation of clutter power and steering vector, etc. A new method is proposed to integrate channel mismatch and internal clutter motion into the clutter simulation. Simulation results show that the proposed simulation method based on prior knowledge of the geographical environment can effectively simulate heterogeneous clutter received by airborne radar.Finally, focusing on the heterogeneous clutter suppression method, the application of segmentation processing and generalized inner product methods are analyzed for heterogeneous clutter suppression. Then a colored-loaded filter method in element-doppler domain is proposed and the performance of clutter suppression under the circumstance of channel mismatch and internal clutter motion is analyzed. Simulation results show that the colored-loaded filter method can improve the performance of radar detection for the interested target.