Overlapped Subarray Design And Beamforming For Array Radars

The appearance of phased array technology enables the same radar to realize multiple functions and perform diversified tasks,thus greatly expanding the functions and application scenarios of radar.However,the thousands of active channels in phased array radar make it expensive.Therefore,cost reduction is an urgent issue while ensuring the performance of phased array radar.Subarray technology provides a feasible solution for low-cost multifunctional phased array.Unfortunately,the continuously regular partition will deteriorate the beam pattern and lead to the decline of radar detection performance,which can not meet the needs of rapid response and multi-task planning.As a new subarray technology,overlapped subarray has attracted extensive attention due to its low cost,modularization and advantages in simultaneous multi-beam performance.In order to achieve the best performance of overlapped subarrays,design and beamforming methods should be carried out according to their application scenarios.This dissertation focuses on the array design and beamforming of overlapped array radar,whose achievements include the following two aspects:1.Beamforming algorithm under regular overlapped structure.Based on the regular overlapped subarray structure which has the equal element distance and subarray size,an iterative optimization model of element-level weights and subarray-level weights is established on the alternating optimization framework.By using the idea of approximation,the non-convex constraints in the model are transformed into a series of convex constraints,and an alternative sequential convex programming algorithm is proposed to design the element-level and the subarray-level weights.In addition,the similarities and differences of the model in the applications of limited field of view scanning,wide-band wide-angle scanning and simultaneous multi-beam are analyzed theoretically,and the maximum scanning ranges of the beam in the three applications are given.Experimental simulations show that the proposed algorithm could suppress sidelobe level effectively.Furthermore,the relationship between the taper efficiency,sidelobe level,beam width and scanning range of the beam pattern is discussed,and the influence of the amplitude error on the performance of the beam pattern is analyzed.Finally,the method is extended to planar overlapped arrays to verify the expansibility and universality.2.The joint design of subarray positions and subarray-level weights based on randomly overlapped subarray.The uniform weighting of the elements and the non-uniform arrangement of the subarrays has the potential to simplify the overlapped subarray structure and keep the low sidelobe.Considering on this structure,the notation of overlapped subarray partition is established firstly.Then,the joint optimization model of subarray positions and weights under limited field of view,wide band and wide angle scanning and simultaneous multi-beam application architecture is established respectively.Then,the alternating optimization framework is adopted to solve this model through two stages.In the first stage,the upper bound of sidelobe level is set,and the sidelobe level is changed from objective function to constraints.Then the zero norm optimization problem of the number of subarrays is relaxed to a norm optimization problem.By utilizing the weighted iterative norm method,this one norm problem could be solved successfully.After this stage,the positions and initial weights are obtained.In the second stage,the convex programming is used to minimize the sidelobe level based on the subarray positions optimized by stage one.Finally,the effectiveness of proposed method is verified by numerical simulations,and the correlations between the subarrays number,amplitude error,the sidelobe level and the taper efficiency are analyzed.