Study On Short Time Suppression Of Nonstationary Ionospheric Clutter

The high frequency over the horizon radar has developed rapidly and its function is very powerful at the beginning of the 21 st century,but its echo inevitably contains nonstationary ionospheric clutter.The clutter will seriously interfere with the detection of the target and reduce the estimation precision of distance,speed and angle.The traditional STAP technology is not effective in restraining the ionospheric clutter as the reason of the inaccurate estimation of the clutter covariance matrix.In order to solve this problem,a short-term suppression method,namely piecewise dimension reduction of the STAP,is proposed in this paper.It is very difficult to study the detailed process of segmented processing,and it is difficult to study the detailed process of segmentation.The phase compensation algorithm can not be studied by hand.If only one dimension to the pulse is segmented in slow time,the equivalent simulation of piecewise STAP,the calculation is small,the process is simple and the feasibility is good,it can be easier to study STAP.Clear and specific processing flow and phase compensation algorithm.Therefore,this paper starts with one dimension and further studies on two dimensions.Great achievements have been made in this study.First,the mechanism of the nonstationary ionospheric clutter is analyzed theoretically,the range of the clutter Doppler frequency is determined,and how the clutter affects the target detection from three dimensions of distance,velocity and angle is discussed,and a model is established for clutter,and a detailed analysis of the clutter characteristics is made.The second discuss the principle of Doppler processing and piecewise Doppler processing,and to deal with the slow time dimension of the data,solve the problem of noise bottom elevation,put forward the phase compensation algorithm,and make the necessary preparation for the segmented dimension reduction STAP.Third,the detailed process of all STAP processing is analyzed,the method of matrix inversion and the estimation of clutter covariance matrix are introduced,and the principle of the local joint processing is discussed in detail.The echo is also segmented to reduce the dimension of STAP,and the phase compensation is carried out by the maximum likelihood estimation and the least two multiplication,and the new method is applied to the electricity.The suppression ability of the separation clutter is obviously enhanced,while the Doppler resolution remains constant and the noise bottom is low,which improves the detection ability of the target and the estimation precision of the azimuth and speed.This study has been completed well.