Tracking loops with time-varying sampling periods for the TH-CDMA signal

Time-hopping signal structure is adopted for overcoming the near-far problem in the Ground-based Navigation System. The signal model of TH-CDMA signal is presented. To track the pulse signals with pseudorandom active-timeslot, tracking loops with time-varying sampling periods are designed. The linear model of the second order TVSP-PLL is presented. The stability of the time-varying model is analyzed based on the First Method of Lyapunov for the linear time-varying system. A transient-response simulation of the second order TVSP-PLL is provided as a verification. The ranging performance of the TVSP-DLL is evaluated. A hardware experiment and a MATLAB simulation are used to verify the noise performance of the TVSP-DLL. The tracking loops with time varying sampling periods are implemented on the FPGA platform and MATLAB. The simulation and experiment results show that the ranging accuracy can achieve centimeter level.