Research On Technology Of GNSS Receiver Robust Broadband Beamforming

Global Navigation Satellite System(GNSS)is widely used in various fields,but the signal power is too weak after the long travel from the satellite to the ground,which makes the system vulnerable to many kinds of interferences.In order to eliminate the effect of interferences on the navigation system and ensure the normal work of it,the paper studies robust wideband beamforming algorithms for GNSS interference eliminations.First of all,the basic theory of beamforming is introduced briefly in this paper,including including the establishment of array signal model and common narrowband adaptive beamforming algorithms.The narrowband and wideband signal models are illustrated separately,and also the array manifold representations of uniformly linear array and circular arrays.Narrow band adaptive beamforming algorithms are introduced,including LMS algorithm,RLS algorithm and LCMV algorithm,brief comparison of the advantages and disadvantages of the three algorithms are made,and the problems of LCMV existed in GNSS applications are also illustrated.Secondly,in order to solve the problems of LCMV existed in GNSS system applications,such as the robustness problem and the burdern of too many constraints,great attentions are paid on the related performance of traditional broadband beamforming algorithms,and a frequency invariant robust broadband beamforming algorithm is proposed in this paper based on traditional beamformers.In order to improve the robustness of traditional beamformers,several common robust beamformers are compared with each other,including the diagonal loading beamformer,the eigenspace beamformer and the worst-case performance optimal beamformer,after which the worst-case performance optimal beamformer is choosen as the base of the beamformer proposed in this paper.Then a frequency invariance broadband beamformer is proposed for GNSS system broadband signal,which greatly reduces the amount of computation and the computational complexity of the algorithm,and by applying the forward-backward smoothing,the robustness of the beamformer is strengthened.Finally,some improvements are made in the proposed algorithm in order to adapt to the needs of GNSS receiver anti-jamming,including applying it on uniformly circular arrays and multi-beam applications.Computer simulations and tests are made to prove the performance of the beamformer,which show that the proposed algorithm can suppress broadband and narrowband interferences,thus the receiver can acquire even if the INR is 70 dB.