Optimization Design And Processing Technology Of Large-scale Thinned Array

As the basic device for effectively receiving and radiating electromagnetic energy in the sensing system,the performance of antenna often plays a decisive role in the overall performance of radio system.Phased array antenna can adjust the direction of beam through "electric scanning" while achieving high gain,so it has been widely used.However,facing the requirements of high precision,low cost and anti-interference,there are still some aspects that need to be improved.Through thinning the array,the aperture of the array can be expanded at the same number of array elements to obtain higher angular resolution.The equal amplitude weighted thinned array can also simplify the structure of the feed system and greatly reduce the cost.In this paper,the design of large-scale thinned array with large aperture is studied,a new method suitable for the design of thinned linear array and planar array is proposed,and the performance of classical optimal beamforming method and DOA estimation algorithm applied to tinned array is investigated.The main research results are as follows:Firstly,the far-field signal model of sparse array is established,the visual range and grid-lobe conditions of pattern are analyzed,the characteristics of two kinds of nonuniform arrays "sparse array" and "thinned array" are summarized.Using the idea of density tapered method,four arrays are designed: density tapered sparse array,uniform random sparse array,density tapered thinned array and uniform random thinned array.The relationship between array performance with elements’ number and sparsity is discussed.Secondly,for thinned linear array design,the proposed population evolution enhanced density tapered method is used to complete the array design under far-field and near-field conditions respectively.Under the far-field condition,the goal of optimization is to minimize the peak sidelobe level(PSLL)of the beam pattern,and good design results are obtained.When the array aperture becomes larger,because the ratio of the distance between the target and the array to the aperture of the array becomes smaller,the original application scenario may no longer meet the far-field conditions.To solve this problem,a new optimization objective function-"energy concentration level(ECL)" is proposed to investigate the energy focusing performance of array imaging results.Combined with the population evolution enhanced density tapered method,a thinned linear array more suitable for near-field imaging is designed.The effectiveness of the proposed method and the optimization objective function for the design of near-field thinned array is verified by imaging the measured data.Then,in order to design thinned planar array,the population evolution enhanced density tapered method is extended to the design of concentric ring array(CRA).A method to quickly determine the number of array elements on each ring according to the density tapered principle is proposed,and the radius and the rotation angle of each ring relative to the center are further optimized by population evolution method,good array design results are obtained.The advantage of this method is that it can set the minimum array element spacing of thinned array,which increases the engineering practicability.Finally,the signal processing method suitable for thinned array is studied.In terms of interference suppression,MVDR and MVDR beamformers are applied to thinned array,and the influence of sparsity on beamforming is analyzed.In order to improve the robustness of beamforming,multiple linearly constrained beamformers,LCMV and LCMP,are applied to thinned linear array to obtain a widened beam,which can overcome the adverse effect of steering vector mismatch.When the constraint direction is the same as the direction of main lobe interference,it can also overcome the phenomenon of main lobe splitting.In the aspect of DOA estimation,the classical DOA estimation methods,such as beam search method,Capon method,MUSIC algorithm,root-MUSIC algorithm and linear prediction method,are applied to estimate the DOA with thinned linear array.Moreover,the performances of several DOA estimation methods are compared and analyzed.