Navigation Satellite Inter-satellite Link Signal Acquisition And Parameter Estimation

To accomplish satellite autonomous navigation,the inter-satellite ranging and establishment and maintenance of inter-satellite communication links are key technology.The Doppler frequency and the uncertainty of transmission delay of inter-satellite link signal are large,and make the signal acquisition more difficult.However,the receiver of inter-satellite link signal can always get some prior information about the received signal assist signal acquisition in practical situations.This paper mainly study prior information assisted acquisition and parameter estimation of navigation satellite inter-satellite link signal.Firstly,this paper proposes an improved signal acquisition algorithm based on the joint code-frequency search,to solve the problem that the signal acquisition in the search scope of Doppler frequency and the code phasewhich is narrowed by the assistant information.Because of correlation peak degradation and the complexities of the limited code-phase search algorithm,we propose the new algorithm based on the joint code-frequency search.The new algorithm also overcomes the problem that the grid of frequencies in the joint code-frequency search algorithm is fixed.Through simulation,we can see that the acquisition performance of the new algorithm is better when the search scope is narrow.Secondly,this paper proposes prior information assisted acquisition method of inter-satellite link signal according to the characteristic of relative motion between satellites.The search scope of Doppler frequency and the code phase which is narrowed by the assistant information firstly in the proposed method,then the signal acquisition is accomplished by the improved signal acquisition algorithm based on the joint code-frequency search.The factors which have influence on the search scope of Doppler frequency and the code phase are analyzed.Through simulation,we can see that the acquisition performance is improved compared withthe conventional signal acquisition methods.Finally,in order to make the search scope of the prior information assisted acquisition method of inter-satellite link signal narrower.The parametric estimation of the inter-satellite link signal based on Kalman filter is proposed in this paper.The measurements about the relative distances and relative velocities between satellites of earlier signal acquisition time are processed with Kalman filter,to get the predictions about the relative distances and relative velocities between satellites of the present signal acquisition time.Then the parameters of the received signal are estimated by the predictions.The simulation results show that the new algorithm can improve the estimation precision of the parameters of the inter-satellite link signal.