Research On Ionosphere Clutter Supression In Hybrid High Frequency Radar Based On Space Time Adaptive Processing

The high frequency hybrid sky-surface wave radar combines the advantages of high frequency sky wave radar and high frequency ground wave radar.Due to the bistatic radar mechanism,the hybrid radar has a complex clutter condition,in which the ionosphere clutter is dominated,affecting the performance of the radar system and the estimation of the sea state parameters.Therefore,the research on the suppression of ionosphere clutter is of great theoretical significance and practical application value for improving the detection ability of radar system for targets.Space-time adaptive processing(STAP)is a clutter suppression method which has been successfully applied to airborne radar.The suppression of ionosphere clutter is studied in this paper based on the hybrid sky-surface wave radar.In this paper,the research status of STAP,hybrid sky-surface wave radar and ionosphere clutter suppression is summarized,which provides a basis for subsequent research.The second chapter introduces the structure of ionosphere,the propagation of electromagnetic waves in the ionosphere and the mechanism of ionosph ere clutter.What's more,the correlationship between contiguous Doppler frequency,angle and distance unit of ionosphere clutter in the hybrid sky-surface wave radar is analyzed.Finally,the sparsity in ionosphere clutter is analyzed.In the third chapter,the principle of STAP is described in detail.The optimal STAP,local joint space-time adaptive method and space-time multi beam method are introduced,and an improved local joint space-time adaptive method is proposed based on the study of the correlationship of the ionosphere clutter.Finally,the algorithm is evaluated by improvement factor and calculation load.In the fourth chapter,the direct data domain method is used to avoid the problem of the inhomogeneity of the ionosphere clutter.A hybrid al gorithm is proposed avoiding the inhomogeneity of the clutter and the computation load of the STAP method is reduced.Finally,STAP based on sparse recovery is applied to the hybrid sky-surface wave radar utilizing the inner sparsity of the ionosphere clutter,and the algorithm is evaluated by improvement factor and calculation load.