The Research Of Clutter Rejection Method Based On The Distinguish Of Target

Sky wave over the horizon radar(OTHR), which can detect ultra long-range target, has the advantages of low cost per unit area, far sight distance, etc., which has been widely used in the detection of ship targets at sea. But as sky wave OTHR achieves target detection by reflection from the ionosphere, the layered structure characteristics and inhomogeneity of ionospheric hugely impact the performance of target detection, meanwhile, the skywave OTHR clutter spectrum wave is broadened due to the ionosphere multimode and multipath effect caused by the ionosphere, detection of the slow moving target in sea surface is severely restricted. In addition, for target detection of ships on the sea will also be impacted by sea clutter. Since slow ship target is similar to the first-order Bragg peak of the sea clutter wave in Doppler domain, the target signal is easily flooded by the strong sea clutter. So the first problem to solve, under the background of sea clutter skywave radar target detection, is clutter suppression of radar echo.Traditional method of clutter inhibition realized by time domain, space domain or frequency domain in order to obtain pure clutter background. However, the traditional method of distinction between target and clutter has a performance bottleneck under the background of complex clutter characteristics. Some clutter has a very similar characteristics and objectives to the target.When the traditional method handled with this kind of clutter, the clutter is treated as a target to remain, resulting in a failure of the algorithm. In recent years, the research on the distinction between the target and the clutter has become a hot issue in the field of clutter suppression. In this paper, we put forward two methods to solve these problems:(1) a method for distinguishing target based on phase space features in a single accumulation period. This method will transform the single accumulation period radar echo into phase space, and get recurrence rate in the phase space. Using recurrence rate to distinguish target.This method is good in real-time, but it can not give the specific information of the target and can not deal with the multi- objective situation.(2) Target discrimination method based on TBD – DPT in multiple accumulation period. This method is based on the pseudo target point which is given by a low threshold detector, using TBD method to relation this pseudo point and protect the points which can form a track. Then using the clutter inhibition method to suppress the clutter. This method can improve the performance of traditional clutter inhibition methods.