Research On Anti-jamming Technology Of Navigation Receiver Based On Spatial Filtering

With the continuous improvement of the positioning accuracy of the satellite navigation system,it plays an increasingly important role in people's production and life.However,because the satellite is far away from the earth,the level of the satellite signal when it reaches the navigation receiver is very weak.The navigation signal received by the satellite navigation receiver is more susceptible to spatial interference,which in turn leads to the navigation receiver being unable to accurately complete the navigation positioning function.Therefore,in order to make the satellite navigation receiver work normally in all kinds of interference environment,it is necessary to study the antijamming technology of the navigation receiver.In this thesis,aiming at the antijamming problem,the spatial filtering structure based on the multi-element antenna was adopted to carry out the adaptive filtering for the spatial suppression interference(single frequency and narrow-band suppression interference),and it finally realizes the filtering of the interference to ensure the normal operation of the navigation receiver.The main contents and achievements of this paper are as follows:Firstly,the structure of anti-jamming navigation receiver is studied.The jamming mechanism of the navigation receiver is analyzed according to the weak points in the signal processing process of the receiver.Through the analysis of various interference types,the adaptive spatial filtering algorithm based on multi-element antenna structure(array)is proposed as the anti-jamming method for the suppression jamming,which acts as the ultramost main and typical type of strong jamming.Next,the direction of arrival(DOA)estimation algorithm based on multi-element antenna is studied.Two DOA algorithms,MUSIC and ESPRIT,are implemented by code simulation respectively,and their advantages and disadvantages are analyzed and compared.In view of the contradiction between the time cost and the accuracy of MUSIC algorithm,a variable step search method is proposed,which can significantly shortens the estimation time on the premise of ensuring the estimation accuracy.A joint method of MUSIC and ESPRIT is proposed to take the advantages of the two algorithms in the estimation time and the estimation accuracy.The joint method can quickly obtain the rough estimation of the signal angle through ESPRIT algorithm,and then obtain the accurate by MUSIC algorithm.This method further weighs the contradiction between the time cost and the estimation accuracy.In view of theinsufficient degree-of-freedom of DOA estimation in the presence of multiple interference sources,the expansion method of the antenna array based on the fourth-order cumulant is discussed.And then,the adaptive beamforming algorithm is studied.The spatial filtering structure and the linear constrained minimum variance(LCMV)beamforming algorithm under the results of spatial-temporal filtering are simulated.Through these simulations,the interference suppression performances under the conditions of different interference numbers and signal-to-interference ratios are observed.It shows the deficiency of the zero depression depth under the spatial filtering structure.Then a spatial-temporal filtering structure is introduced,and contrast experiments of the same algorithm under the new structure are performed.Simulation result shows the performance is obviously improved,in which the zero depression depth is reduced by about 10 d B,which can effectively suppress the jamming in the presence of multiple interference.Finally,the above research results are integrated into an anti-jamming simulation platform of navigation receiver.The main development work includes the interface file reading and writing module,simulation data generation module,DOA estimation and beamforming algorithm module,and result demonstration module.According to the results of the platform,the signal to interference ratio of the received hybrid signal processed by the algorithm can meet the requirements of anti-jamming tolerance when the navigation receiver works normally.