Research And Implementation Of Navigation Signal Tracking Technology In High Dynamic

Satellite navigation technology has become an essential part of the development of society. In some special areas, as the larger relative velocity, acceleration and jerk between the receiver carrier and the satellite, the received satellite signal will contain a large Doppler frequency, change rate of Doppler frequency and even the secondary change rate of Doppler frequency, which will bring difficulties and challenges to signal tracking. This paper takes the GPS signal as an example, studies tracking algorithms for high dynamic navigation signal, and completes the FPGA implementation of related algorithms.This paper firstly introduces the structure of GPS signal and Doppler’s characteristics, and gives the high dynamic model of navigation signal, which provides model base for the later algorithm simulation. Then, according to the high dynamic model, a method which can directly synthesizes the high dynamic signal in the digital domain is given, which provides the basis for the generation of the high dynamic GPS signal. Aiming at the problem of signal tracking in high dynamic environment, based on navigation signal processing and traditional tracking method, this paper carries out the following algorithm research works:(1) Third-order PLL is used to track carrier. The results show that third-order loop has shortcomings and limitations when tracking GPS signal carrier in high dynamic.(2) Carrier tracking schemes based on Kalman filtering techniques is studied, including the LKF algorithm using phase detector, EKF algorithm linearizing coherent integration output and UKF algorithm approximating the distribution of coherent integration output, and these carrier tracking algorithms are simulated and analyzed. Simulation results show that, under high dynamic model proposed in this paper, the loss-of-lock threshold of EKF and UKF is lower than the LKF algorithm, in the case of the same carrier to noise ratio(CNR), the frequency RMS error of UKF algorithm is slightly smaller than the EKF algorithm.(3) Two schemes for joint tracking of carrier and spread spectrum code on the basis of the carrier tracking is provided. One is fifth-order LKF tracking scheme, the other is joint tracking scheme which combines carrier UKF and code third-order loop filter. Two algorithms are compared through simulations, and the results show that the tracking algorithm which combines carrier UKF and code third-order loop has lower steady-state tracking error.Another important work of this paper is the implementation of high dynamic GPS relevant tracking algorithm based on the hardware platform of FPGA. Considering the scope and precision, the 32 bit single precision floating point format is applied in the calculation of Kalman filter equations. After the design and simulation of each module, the overall design scheme and implementation results are given.