Research On Incoherently Distributed Source Direction Finding And Positioning Technology

The point source model is usually assumed in traditional array signal processing.In fact,due to the influence of multipath and other factors,the received signals often show certain angle expansion characteristics.Therefore,the distributed source model is introduced to solve the problem of performance degradation caused by model inconsistency.According to the signal characteristics,it can be divided into coherently distributed source and incoherently distributed source.Incoherently distributed source is more complex than coherently distributed source,so the conesponding processing is more difficult.With the development of hardware equipment,the reconnaissance of incoming signals includes not only angle estimation,but also positioning of the target.The direction finding and positioning algorithm for incoherently distributed source is studied in this thesis.Firstly,the influence of incoherently distributed source on the traditional point source direction finding algorithm is analyzed in this thesis.Then,the direction finding algorithm of incoherently distributed sources is investigated.Finally,the localization algorithm under the incoherently distributed source model is introduced.The main research contents and achievements are as follows:1.The direction finding error of ESPRIT algorithm under point source model is inversely proportional to the distance between subarrays.Due to the limitation of phase ambiguity,the distance between subarrays cannot exceed half wavelength,otherwise the direction finding range will be reduced.Therefore,a modified ESPRIT algorithm based on multilevel concatenation is proposed in this thesis.The proposed algorithm is immune to the problem of angle measurement range reduction caused by phase ambiguity.Compared with the traditional ESPRIT algorithm,the proposed algorithm improves the direction finding accuracy without significantly increasing the computational complexity.2.When the source is incoherently distributed,the signal subspace of the received signal is expanded,and the noise space is compressed,which leads to a sharp decrease in the maximum number of distinguishable targets in the array.Therefore,an incoherently distributed source direction finding algorithm based on fourth-order cumulant is proposed in this thesis.The proposed algorithm can increase the maximum number of distinguishable targets without changing the array structure,so the multi-target direction finding problem with limited array structure can be solved by using this algorithm.3.At present,there are few localization algorithms for incoherently distributed sources.In view of this situation,two direct postioning algorithms of coherently distributed source models are modified to suit incoherently distributed sources in this thesis.However,both methods require multiple direction finding stations.In order to reduce the number of direction finding stations,a cross positioning algorithm for incoherently distributed sources using array cross correlation is proposed in this thesis.For the proposed algorithm,the influence of uncorrelated scattering components on direction finding is weakened,and the fuzzy point problem in multi-source cross positioning is solved.Therefore,the proposed algorithm only needs two direction finding stations to estimate the source position in space.