| In the face of increasingly complex environments of warfare,helicopters have gradually become indispensable weapons and equipment in modern three-dimensional warfare with their good maneuverability and outstanding ultra-low-altitude combat capabilities.Due to the low flight altitude and slow flight speed of the helicopter,the terrain environment it faces is complex and changeable,and strong ground clutter will seriously affect the radar’s detection of ground targets.The research of radar clutter suppression is becoming more and more important.This thesis mainly studies the clutter modeling and signal processing problems of helicopter-borne radars,introduces the clutter modeling methods under the helicopterborne platform,and analyzes the clutter characteristics under different terrains,and gives the helicopter-borne radar signal processing method.The main content of this article is as follows:1.Established a sub-array signal model and a target echo signal model for the helicopterborne radar.Starting from the azimuth information and undulating characteristics of the clutter,the clutter model was gradually derived using the equidistant ring method.Finally,combined with simulation analysis of different terrains Characteristics of the clutter spectrum.2.Explain the basic principles of signal processing for helicopter-borne radars,give the procedures of non-adaptive signal processing and space-time adaptive processing(STAP)under the helicopter-borne platform,and then address the problem of excessive STAP calculations,Introduced two dimensionality reduction STAP methods,JDL and mDT,and finally realized the modeling and analysis of the helicopter-borne radar signal processing system through simulation.3.Aiming at the close-range target detection scene of helicopter-borne radar,the clutter distance dependence problem is introduced according to the angle-Doppler relationship,and the phenomenon of clutter spectrum broadening brought about by this is shown in combination with simulation analysis.Then,the methods of clutter compensation under the helicopter is given,such as Principles of Doppler Warping(DW),Angle Doppler Compensation(ADC)and Adaptive Angle Doppler Compensation(A2DC).Finally,the performance of the three clutter compensation methods is compared through simulation.4.Aiming at the long-distance target detection scenario of helicopter-borne radar,the distance ambiguity phenomenon caused by the mutual aliasing of echo signal pulses is introduced,and the clutter spectrum of different heavy ambiguities is simulated and analyzed.Then,a design method of non-adaptive pitch-dimensional filter using radar information is given.In view of the large jitter of the helicopter-borne platform and the strong platform unsteadiness,the design principle of the adaptive pitch dimension filter is given.It extracts the characteristics of the close-range clutter area by constructing the auxiliary channel in the angle-Doppler domain,and makes it cancel with the main channel to adaptively suppress the close-range clutter.Finally,combined with simulation experiments,the performance of the two close-range clutter suppression methods in different scenarios was compared and analyzed. |
