The Research On Fast Direction Finding Technology Based On Spatial Spectrum Estimation

The battlefield electromagnetic environment is complicated in modern electronic warfare and the traditional passive direction finding technology can not meet the requirement of people in some cases. Compared with the traditional direction finding technology, the spatial spectrum estimation direction finding technology is characterized by high precision, high resolution etc. However, the practical application of spatial spectrum estimation in electronic warfare still faces many problems. According to two promblems about the general spatial spectrum estimation algorithms could not be solved fast and cannot estimate coherent signal, the spatial spectrum estimation algorithms which can be applied to modern electronic warfare are discussed in this thesis. The main research contents of this thesis are as follows:Firstly, the basic structure of spatial spectrum estimation direction finding system was analyzed and the receiving signal mathematic model of uniform linear array is established, which providing theoretical basis for spatial spectrum estimation algorithm.Then, the Minimum Variance Distortionless Response algorithm and Multiple Signal Classification algorithm which are ones of most common spectrum estimation are deduced and their DOA(Direction Of Arrivals) estimations are simulated. The results of simulation show that the performance of the Multiple Signal Classification algorithm is superior to Minimum Variance Distortionless Response algorithm.Combined with the the theory of adaptive signal processing and the principle of beam nulling, the beamforming nulling DOA esitimation algorithm which can be sovled by fast iterative method is proposed. Compared with the Multiple Signal Classification algorithm, the simulation of DOA estimation and the simulation of precision statistics under different signal-to-noise ratio simulation are run in the computer. The simulation results show that the beamforming nulling DOA estimation algorithm and Multiple Signal Classification algorithm can estimate the incident directions of signals and the estimation accuracy of beamforming nulling DOA estimation algthrim is equal to that of Multiple Signal Classification algorithm in certain cases, but the proposed algorithim requires less compution.On basis of analysis of the current commonly spatial smoothing algorithms which can estimate coherent signals, the proposed beamforming nulling DOA estimationalgorithm is improved and the spatial smoothing algorithm based on beamforming nulling DOA estimation which can estimate coherent signals is obatained. Compared with the Multiple Signal Classification algorithm after spatial smoothing processing, the DOA estimation of coherent signal simulation on computer is run. The simulation results show that there are peaks on incident directions of signals in the spectral functions of improved algorithm and Multiple Signal Classification algorithm after spatial smoothing, but the solution process of improved algorithm is easier.In this thesis, the proposed beamforming nulling DOA estimation algorithm can effectively solve the problem that the computation quantity of most common spatial spectrum estimation algorithm is great and its improved algorithm which can estimate coherent siganals can effectively solve the problem that most common spatial spectrum estimation algorithm cannot estimate incident direction of coherent signals.