Research On Direct Position Determination And Site Layout Optimization Based On Coprime Array

Compared with the traditional two-step positioning method,The Direct Position Determination has the advantages of excellent performance in low signal-to-noise ratio(SNR)environment and no parameter correlation.The increasingly severe electromagnetic environment makes the direct positioning of multiple radiation sources with high precision and high resolution become a major research focus in this field.Due to the limited degree of freedom and estimation accuracy of using uniform linear array,coprime array is introduced into the DPD method of radiation source,and the unique advantages of coprime array are used to improve the positioning performance.In addition,for multi-base station passive positioning system,the layout of the site also affects the positioning performance of the positioning system to some extent.Therefore,this paper studies DPD and the optimization method of site layout based on coprime array.The main work and research results are as follows:1.On the basis of constructing a DPD model,a single emitter DPD method based on the Maximum Likelihood(ML)and a multi emitter DPD method based on the Multiple Signal Classification(MUSIC)algorithm were studied.Detailed analysis was conducted on the evaluation indicators that measure the performance of the localization system,such as Root Mean Square Rrror,Cramer-Rao Lower Bound and Geometric Dilution of Precision.Finally,the simulation results show that the performance advantages of direct location of radiation source are compared with the traditional two-step location method under low SNR.2.The coprime array is applied to DPD.Aiming at the problem that the DPD method based on coprime array has low utilization rate for virtual array elements,a DPD method of coprime array based on covariance matrix reconstruction(CMR-DPD)is proposed.The covariance matrix of array signals is extended to obtain a Toeplitz matrix with missing data,and the zero elements in the matrix are recovered by low-rank matrix reconstruction theory.Finally,the positioning result is solved by subspace class algorithm.This method achieves100% utilization rate of virtual array elements,further increases the aperture of virtual array,and improves the positioning accuracy and resolution performance in the environment of less snapshots and low signal-to-noise ratio,with better robustness.3.Based on the analysis of the two-step passive location system,the research on site layout optimization is further extended to DPD.In order to make the positioning effect of radiation source targets in the controlled area better,an optimal location strategy with GDOP as the evaluation index is proposed.The Cramero lower bound of DPD is analyzed in detail,and GDOP is obtained according to CRLB of DPD.On this basis,the optimal station layout model of DPD system is established and Particle Swarm Optimization is used to solve the problem.The optimal station layout scheme of three base stations in a specific environment and the influence of different station layout patterns on the DPD performance under the condition of four base stations are analyzed by simulation,and the appropriate station layout scheme is given according to the actual positioning environment.