Research On Mutual Coupling Correction Technology Of Adaptive Array Antenna In Plasma Environment

When the reentry body reenters the atmosphere,due to high temperature ionization,a layer of plasma sheath will be wrapped around the reentry body.The plasma sheath will have a serious impact on the navigation signal,which will cause the power of control signals such as navigation and guidance to decline sharply,and in serious cases will cause the communication interruption between the reentry body and ground station or satellite.This phenomenon of communication interruption is called "blackout".In order to weaken the influence of "blackout" on signals,scholars at home and abroad have done a lot of research.The development of beamforming technology provides feasibility for solving "blackout" problem.The array antenna composed of multiple antenna units is used to improve the signal receiving gain,so that the receiver can work under lower energy and signal-to-noise ratio.In the application of beamforming technology,how to solve the influence of mutual coupling and multipath error in plasma sheath environment has become the focus of this paper.Under the support of the National Natural Science Foundation of China "Study on the Influence of Plasma Sheath on Satellite Navigation Signals and the Method of Beam Formation Suppression",this paper studied the problems mentioned above.It analyzed the characteristics of the complex symmetric strip Toeplitz property of the mutual coupling matrix,and a DOA estimation algorithm is proposed to eliminate the influence of mutual coupling under the condition of plasma sheath.Under the condition of mutual coupling error,the algorithm solves the influence of rank deficit on positioning accuracy and only needs one-dimensional search to get DOA of incident signal.The main content of this paper is as follows.Firstly,the mathematical model of array antenna is introduced in detail,the array model under the influence of mutual coupling error is analyzed,and the advantages and disadvantages of various methods to solve the influence of mutual coupling error aresummarized.The blind calibration method based on array signal processing is chosen to solve the multipath error caused by plasma sheath environment.This kind of algorithm can carry out DOA estimation while solving the influence of mutual coupling error.In this paper,decoherence processing is carried out in the DOA estimation process to achieve the purpose of correcting multipath error.The cause of multipath effect in plasma sheath environment is introduced,and the mathematical model for multipath error is established.According to the analysis of the mathematical model,the general DOA estimation algorithm has failed due to rank loss in the coherent environment.The principle of spatial smoothing algorithm and the improved spatial smoothing algorithm are introduced in detail.The mutual coupling error and multipath error are corrected to obtain the array model and covariance matrix in the plasma sheath environment.The Toeplitz structural characteristics of the mutual coupling matrix are analyzed to transform the mutual coupling matrix.The mutual coupling coefficient is separated by matrix transformation.Then a simple linear constraint is applied to transform the extremum problem of spatial spectrum into a quadratic programming solution problem,which reduces the computational burden of the algorithm.Matlab numerical simulation software is used to do the simulation comparison the algorithm in this paper with others.From spatial spectrum simulation,comparison of angle measurement,the comparison of angle measuring success probability and other aspects to evaluate the algorithm in this paper and verify that the algorithm is valid.In the simulation comparison of spatial spectrum,it can be clearly seen that the algorithm in this paper has a sharp peak and can effectively identify the direction of incoming wave.In the case of different SNR and different number of beats to compare the angle measurement accuracy and success probability of different algorithms,the conclusion can be drawn that the algorithm in this paper has a better angular measurement performance.Finally,the three-dimensional model of the array in the plasma sheath environment is established by using Ansoft three-dimensional numerical simulation software.The realflight data are input to simulate the receiving state of the receiver in the plasma sheath environment.The calibration information estimated by the algorithm is used to correct the array antenna.The validity of the algorithm is verified by comparing the pattern before and after calibration.Four kinds of flight data at different flight altitudes are set in the experiment.The main lobe of the array antenna is recovered and improved after calibration,which can prove the generality of the algorithm.