A Study For Multi-Arrays Anti-Jamming Algorithm Based On Adaptive Antenna

Satellite signals are emitted from distant space.They are vulnerable to noise or interference from the jamming machine when they arrive at ground receiver terminal through the complex electromagnetic environment.So it is impossible for users to receive satellite signals correctly.Therefore,it is important to study how the receiver filters out the oppressive jamming and improve the accuracy of navigation reception.This thesis focuses on how the satellite navigation receiver adjusts the optimal weight vector adaptively to make the null point to the direction of the suppression interference,and adapts to the complex environment.The points of this paper are as follows:(1).Research on the basic theory of satellite navigation system.Deduce of several spatial filtering optimization criteria.Provide several indicators to measure anti-jamming performance.(2).It is verified by simulation that the traditional linearly constrained minimum variance criterion can't deal with coherent signals.So an improved algorithm based on vector reconstruction algorithm is proposed to solve this problem.The suppressed coherent interference can be divided into completely coherent interference and incompletely coherent interference.For completely coherent interference,the interference subspace can be extended to the virtual interference subspace,and then be grouped.For incompletely coherent interference,the coherent interference subspace is extended to the virtual subspace and transformed to be completely coherent by the change factor to extract.(3).Analyze the objective function in the linearly constrained minimum variance criterion.Construct the interference subspace to replace the autocorrelation matrix,which not only reduce the loss of satellite signal but suppress the oppressive jamming well.When we put the decoherent interference space reconstruction matrix into the improved linear constraint minimum variance criterion to obtain the optimal weight vector.The proposed algorithm can accurately estimate the angles of coherent interference and form the nulls in the direction graph.(4).This thesis proposes two improved algorithms for null widening and deepening and a method to construct discrete signal model.One is to add discrete signals near the direction of the interference,then,use the change matrix to deepen the null of discrete signals and interference.Combine these two models into linear constraint minimum variance criterion.The second is to construct the fourth-order cumulant matrix of discrete signals.It verified that both algorithms can realize deepening and widening of nulls in the direction graph at the same time.Among them,the method based on the fourth-order cumulant can process coherent signals,but its calculation is so large.The implementation is more complicated when we construct the model of oppressive jamming.