Research On Digital Beamforming Algorithms At Subarray Level

Phased array radar antenna is large-scale and has a large number of array elements.In order to reduce the cost and the computational burden,so the processing at subarry is usually adopted.Through a reasonable subarray division,reducing the number of digital channels,combined with adaptive beamforming,the interference can be suppressed by the adaptive weight at the subarray level.In addition,with the continuing development of the phased array technology,wideband phased array radar technology has gradually become an important research direction,time delay technology and subarray division technology are a worthy methods to extend the instantaneous bandwidth of the phased array antenna.This paper firstly introduces the model of the phased array antenna,and analyses the method of narrowband and wideband beamforming.And several basic adaptive algorithms such as the linear constrained minimum variance,the least squares algorithms,etc.are introduced to analyses the theory and compare the performence.At the same time,the SINR performance of SMI and LSMI algorithm is simulated and compared to verify the effectiveness of the diagonal loading technique.Then,the method of partitioning array is introduced,focusing on the adaptive beamforming method of nonuniform adjoining subarray,the method of noise normalization is used to suppress the increased sidelobe level due to the unequal power of output noise of the subarray level of the nonuniform adjoining subarrays Level.Aiming at the problem of the main lobe distortion and sidelobe increase under small snapshots,a subarray-level adaptive beamforming algorithm based on SVD constraint and an adaptive algorithm,combining SVD and penalty function constraints are proposed to effectively keep the mainlobe,reduce the sidelobe to maintain a good performance of adaptive pattern.The subarray array thinned pattern is introduced,the subarray thinned pattern algorithm based on harmony search algorithm is proposed,and the sparse array is optimized from the subarray level to reduce the sidelobe level effectively.Finally,this paper introduces fractional delay compensation to design wideband digital array beamforming.In order to solve the problem of beam pointing offset caused by traditional narrowband phase shift processing method and integer delay method,it is necessary to study sampling delay based on fractional delay Wideband Beamforming Technique.Some design methods of fractional delay filter based on FIR and all-pass are discussed,and the amplitude and group delay characteristics of two design methods are compared and analyzed.The characteristics of the directional pattern of wideband beamforming based on fractional delay are discussed under different bandwidth and sampling rate.In order to further reduce the complexity and cost,sub-array fractional time-delay broadband beamforming is carried out.Simulation shows that the sub-array delay can be effectively carried out by suitable sub-array division.