Research And Implementation On The Evaluation Technology Of BPSK And TDDM Based Navigation Signal Quality

The Global Navigation Satellite System(GNSS) has become an indispensable part of world development. Navigation signal abnormalities such as clock jitter, power error will directly affect the positioning and timing services of the system. Therefore, only the effective evaluation of GNSS signal quality can ensure the satellite navigation system operation stably.The Binary Phase Shift Keying(BPSK)(10) modulation and Time Division Data Modulation(TDDM) are gradually applied to new navigation system with better signal performance and positioning accuracy. But the existed evaluation system lacks the compatibility for the BPSK(10) and TDDM signal. Besides, because the existed signal evaluation system is mostly built on the ground, the evaluation system does not know whether the exceptions are caused by the satellite signal source or the propagation environment. Besides, the analysis of the data is offline signal analysis, and cannot generate warning when there is an exception in time. Therefore, this thesis completes a design of real-time satellite signal source evaluation platform based on the BPSK(10) and TDDM modulation.Firstly, the frequency spectrum and correlation characteristic of BPSK(10) and TDDM are analyzed, based on the signal generation schemes. Then the basic principle of baseband signal processing algorithm is elaborated, including the correlation methods in both time domain and frequency domain using FFT as well as the tracking method and principle of loop filter. Two new correlation method named Insert 0 and Insert 1 are proposed for the TDDM signal processing. Then, the importance of the signal parameters such as pseudo-range, carrier phase, carrier frequency and carrier-to-noise are analyzed. And the appropriate methods measuring these parameters are designed based on the principle of receiver. C program is written to verify the feasibility of these methods. Finally, the evaluation algorithm is programmed and debugged on the FPGA hardware platform. The implementation of each module of the baseband signal processing and parameter evaluation is discussed in detail. The platform measures the four critical parameters of both BPSK(10) and TDDM signal in real-time. The results show that the evaluation platform can work as the expected requirement.