Research On Adaptive Navigation Anti Jamming In Pseudolite Environment

Pseudo-lite technology has received extensive attention and widespread application in various fields since it was put forward.Usi ng pseudolites to position separately or in combination with navigation satellites has been of the significant method to improve the performance of navigation system.However,the near-far effect is still one of the urgent problems in pseudolites.The existing solu tions are based on the change of the transmitter signal structure or the ch ange of the receiver correlator,which makes the receiver's versatility poor.Nonetheless,array signal processing has received great achievements in the pas t few decades,in which adaptive b eamformmings are widely used in the field of navigation and anti-jamming.With the combination of adaptive array processing and pseudo satellite near-far effect problem,this paper has taken much in-depth study on the adaptive anti-jamm ing technology in pseudolite environm ent,which mainly includes the following aspects.(1)For the lim itation of the existing satellite navigation system,we discuss the necessity of pseudo satellite enhanced positioning,expound the causes and im pact of pseudolites near-far effect,and make a detailed analysis of shortcomings of the existing solutions.(2)With the combination of adaptive array processing and pseudolites near-far effect problem,a multi-constrained beamforming method in pseudo-lite environment is proposed.The method is used to suppress the signal power intensity of pseudolites by optimizing the beam direction,which makes it consistent with the navigation signal,to ensure navigation signals and pseudo satellit e signals can be captured norm ally.At the same time,this m ethod achieves m aximum interference signal filtering,thus the navigation receiver works normally under the concurrence of pseudolite signals,strong interference signals and navigation signa ls.Digital simulation experim ents and performance analysis show that the proposed method is effective.(3)In the p resence of sig nal direction estimation errors and the beam pattern distortion,we propose new robust beam forming algorithm.Firstly,the interference covariance matrix is re constructed,and then the reconstr ucted covariance m atrix is projected to the noise subspace,so that the optimum projection of the desired sig nal steering vector in the noise subspace can be achieved,and the diagonal lo ading factor? is accurately solved.The computation of the proposed algorithm is less than RCB and WCPO m ethod,which im prove calculation accuracy of the load factor ?.Practical simulation results show that the proposed m ethod overcomes the problem of signal direction estimation errors effectively,reduces beam pattern distortion,and has a lower beam side-lobe gain than RCB and WCPO algorithm.(4)In view of the problem that the pe rformance of adaptiv e beamforming is severely degraded in th e presence of a rray platform jitter or interference m otion,the existing solutions are discussed and analyzed in detail,and the shortcomings are pointed out clearly.Then,a new null broadening m ethod based on the interference covariance matrix reconstruction is put forward.In the proposed method,the standard Capon spatial spectrum is firstly expande d by convolving with a window function.Subsequently,the extension Capon spatial sp ectrum is utilized to reconstruct the covariance matrix.In addition,the proposed adaptive diagonal loading m ethod is used to estimate the signal optim al vector.Simulation results dem onstrate the proposed algorithm has excellent output SINR performance and good robustness against direction mismatch,angle vibration and m otional interferes,which outperform s other existing adaptive beamformers.(5)Finally,we put forward the im plementation scheme of anti-jamming system in the pseudolite environment,introduce the design methods of key modules in the system,and provide the DSP software design flow and the communication protocol and m ode between DSP and FPGA.Si mulation experiments and joint sy stem test sho w the engineering practicability of our method.