Research On Optimized Acquisition And Tracking For BeiDou QPSK Signal

The GNSS(Global Navigation Satellite System) has been widely used and considerablydeveloped in economy, defense and other fields since it’s bone. BeiDou system has been put into userecently after many years’ development. But as a kind of satellite-based radio navigation system, theperformance of BeiDou system can be easily effected by the quality of received signals, theenvironment in which the receiver is in and some other factors. As the first two steps of GNSS,acquisition and tracking are keys to improve the GNSS performance. In order to make the receiver ofBeiDou navigation system work better, this dissertation studies on acquisition algorithms and trackingalgorithms based on the analysis of signal structure of BeiDou system, and a simulation platform isset up for performance verification.Firstly, the principle and method of QPSK technology is analyzed, and a model of intermediatefrequency (IF) signal is made considering the structure of BeiDou B1QPSK signal and the errorscaused by signal transmission. Based on the model of IF signal, according to the structurecharacteristics of the signal, a dual-channel parallel code phase search acquisition algorithm isproposed, and this algorithm can work successfully and efficiently in detection of BeiDou signal.Quick acquisition algorithm aided by inertial information is proposed to meet the need of quickre-acquisition as the receiver lost useful signals in high dynamic environments, and solve the problemof signal leakage caused by high dynamic movement of receiver. And an optimized high sensitiveacquisition algorithm which involves coherent and incoherent methods is made to solve the problemof acquiring weak signal of BeiDou navigation system. Above two both make great improvements ofBeiDou acquisition algorithm.Then the dissertation studies on signal tracking, which is the next step in signal processing afteracquisition. Based on analysis of relationship between parameters and performance of tracking loop, amethod which can adjust parameters like loop order, loop bandwidth of tracking loop in time isbrought forward in order to make the least error of the tracking loop.In order to estimate the states in tracking loop precisely, a design of tracking loop based onkalman filter and states feedback control is analyzed. The design makes it possible to track signalsuccessfully and limits the loop error around zero at the same time. To simplify the tracking loopfurther, EKF and UKF are put into use which take I_P, Q_P as observations, which can let the loopget rid of phase discriminator. Besides, the tracking loop with nonlinear kalman filter can improve the tracking performance in high dynamics, which can also be useful in design of new kinds of trackingloop.Finally, a simulation platform including both signal generation and signal processing isperformed, which can verify the performance of algorithms studied above. Considering the structureof the system and expandability, a design of the signal processing platform on FPGA is given forrealization in the near future.