| GNSS navigation signal is an important part of satellite navigation systems, and it affects the reliability and accuracy of position, navigation and time service directly.With the development of navigation systems and improvement of users’ requirements,navigation systems needs to provide more types of services. To meet different types of requirements and break the constraint of limited frequency band of the navigation system, the navigation satellites will send more signals in the same band. Meanwhile the limited power of the HPA and nonlinear characteristics of the transmission channel, the navigation satellites needs to send high-power efficiency and constant-envelop signals. Because of the above reasons, it is necessary to do deeper research to the multiplexing technology.This paper focuses on simulation analysis of Galileo E5 signal and GPS L1 band signals. It contains:(1)A detailed study of the generation mechanism of Interplex method, CASM method, POCET method is given. Analyzing the characteristics of each modulation scheme and the calculation method of multiplexing efficiency of each modulation scheme is also provided.(2)This paper studies the assessment criteria of the navigation signal. The principle of the code tracking loop is given. The assessment methods including code tracking loop accuracy, Gabor bandwidth and multipath error is provided. The criteria for assessing the multiplexing method including multiplexing efficiency, combinng losses and peak to average power ratio is also present.(3)This paper analyzes the influence on performance of POCET multiplexed signal,Interplex signal and Galileo E5 by the bandwidth of the filter. The simulation of multiplexed signal which contains the GPS L1 frequency band BPSK(1), BPSK(10),BOC(1,1) modulation signal is given. Multiplexing efficiency of the above signals filtered by diverse bandwidth filters is provided.(4)This paper analyzes the filter bandwidth’s impact on phase detector output curve and S-band loop tracking error of the three branches Interplex multiplexed signal, four branch Interplex multiplexed signal, four branch POCET multiplexed signal and navigation system Galileo E5 signal.The detailed analysis of the S-curve and tracking error of the Interplex signals and POCET signals when the signals are filtered by the filter the bandwidth of which is 40 MHz is provided.(5)In this paper, a detailed analysis of the impact on variation of multiplexing efficiency, peak to average power ratio and the tracking error performance of the Interplex signal, PCOET signals and the Galileo E5 signal when deviation between the I and Q signal path navigation ranging code phase happened. We find that I and Q branch code phase deviation of the combined signal has little impact on the multiplexing efficiency of the Interplex signal and POCET signal, but has large influence on the multiplexing efficiency of the Galileo E5 signal. |
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