Research On The Method Of Subarray Division And Side-Looking Planar Array Clutter Suppression For Airborne Phased Array Radar

There are a lot of ground clutter in the airborne phased array radar echo when it is looking down,which seriously affects the performance of radar moving target detection.Space-time adaptive processing(STAP)effectively suppress clutter by forming clutter-matching notches in space-time two-dimensional plane.But in practical application,airborne phased array radar STAP still has some problems to be solved.First of all,in order to detect long-range targets,modern phased array radars have a large antenna area,usually consisting of dozens or hundreds of columns of array elements and STAP at array element level is diffcult to implement due to its high dimension.Secondly,the space-time distribution of the short-range clutter of the side-looking planar array changes rapidly with distance,showing strong range nonstationarity.STAP is difficult to select enough independent identically distributed samples to estimate the covariance matrix,resulting in poor clutter suppression performance.Some researches have been done in these two aspects,but in the subarray division of airborne radar with large array,the flexibility of digital array arbitrary composite subarray and the clutter distribution characteristics after Doppler dimension reduction have not been fully considered,so it is difficult to ensure the superior clutter suppression performance in various environments.In the short-range clutter suppression of side-looking planar array,the superior clutter suppression effect can be obtained only when the clutter is not range-ambiguous or when there are many pitch elements,but the processing performance is not ideal when the clutter is range-ambiguous and the pitch element is insufficient.Therefore,the above two problems should be further studied.This paper studies the above problems.In the aspect of subarray division of airborne radar with large array,a subarray division method based on clutter space-time distribution characteristics is proposed,which makes full use of the clutter distribution characteristics after Doppler dimensionality reduction and the flexibility of digital array arbitrary composite subarray to design matching division for different clutter environments,and improves the division efficiency and processing performance of subarray level STAP.In the aspect of short-range clutter suppression,a pitch filtering method based on short-range clutter range compensation is proposed,which compensates different pitch frequencies for different range samples when estimating the pitch covariance matrix of each range gate,making the covariance matrix estimation more accurate and improving the performance of short-range clutter suppression.The main content of this paper can be summarized as follows:1.The subarray division method of airborne radar with large array is studied.A new spatial dimension reduction method based on subarray partition is proposed for digital array radar using doppler domain dimensionality reduction STAP.In this method,the prior knowledge of radar parameters and flight state is used to obtain the clutter distribution in each Doppler cell,and the notch forming ability of the divided array is taken as the evaluation index of the subarray division.The intelligent algorithm is applied to search the subarray division scheme,which not only makes the division independent of the echo data,but also significantly reduces the computation.Simulation results show that the proposed method has good clutter suppression performance in various clutter environments.2.The short-range clutter suppression method of side-looking planar array is studied.Aiming at the problem that the main lobe of the beam formed by existing pitching filtering methods is easy to deform and the performance of short-range clutter suppression by using radar first pulse echo to solve pitch weight vector is poor,a pitching filtering method based on range compensation for short-range clutter is proposed.The method estimates the pitch covariance matrix for each range gate requiring pitch filtering and solves the pitch weight vector by using radar first pulse echo.In the estimation of each covariance matrix,different pitch frequencies are compensated for the samples with different distances,so that the pitch frequence of the samples with different ranges is consistent with that of the units to be processed,and the covariance matrix is estimated more accurately.Simulation results show that the method is effective in suppressing short-range clutter.