Research On Robust Beamforming And Interference Mitigation Algorithm For Satellite Navigation

Satellite navigation system can provide users with all-weather positioning,navigation and timing functions.At present,it has been widely used in various industries.However,for the civil navigation system,due to the openness and transparency of its signal structure and the increasingly complex electromagnetic environment,malicious interference against the navigation receiver emerges one after another.Therefore,it is particularly necessary to study the anti-interference technology suitable for the navigation receiver.However,in the time-frequency domain,the interference signal is easy to camouflage but not easy to be distinguished.Therefore,the spatial anti-interference technology based on beamforming method can be adopted.Thesis studies the robust adaptive beamforming algorithm for navigation receiver.At present,most research on beamforming algorithms is based on minimum variance distortionless response(MVDR)criterion.The ideal optimization problem constructed by this criterion needs the accurate steering vector of desired signal and the interference plus noise covariance matrix without desired signal components.However,there are multiple error scenarios in practical application,which will lead to the mismatch of the steering vector of the navigation signal.Besides,as the interference plus noise covariance matrix cannot be obtained directly,it is usually replaced by the sample covariance matrix.The above two cases will lead to the severe degradation of the output performance of the beamformer.Therefore,thesis proposes robust beamforming algorithms with good output performance from two aspects: steering vector correction and interference plus noise covariance matrix reconstruction.The main research contents include:Aiming at the mismatch problem of the steering vector of navigation signal,thesis proposes to obtain the correction value of the steering vector of navigation signal by solving a convex optimization problem.The key lies in the construction of convex optimization problem.Thesis constructs a new convex optimization problem by setting a new constraint condition,and then the steering vector of navigation signal is corrected.Experiments demonstrate that the proposed beamforming method based on steering vector correction has good output performance and algorithm robustness.To obtain the interference plus noise covariance matrix and avoid the degradation of the output performance of the beamformer under the condition of high signal-to-noise ratio,thesis proposes two covariance matrix reconstruction methods from two aspects.The core of the two algorithms are the accurate estimation of the power of each interference and the construction of the projection matrix of the array received signals,respectively.Both methods can effectively eliminate the navigation signal components in the covariance matrix,and then the accurate interference plus noise covariance matrix can be obtained.Experiments show that the two proposed beamforming methods based on covariance matrix reconstruction both have perfect algorithm robustness and good output performance.