| As the built Global Navigation Satellite Systems(GNSS) modernizing and new systems developing, more and more signals occupy frequency bands used for GNSS, the spectrum of different signals transmitted by the same system and the spectrum of signals transmitted by other systems overlap each other, navigation interference between signals become severe, so the radio frequency compatibility issues become sharp focus. In addition, the high power amplifier non-linear effects on the performance of navigation systems are questions that can not be ignored, the satellite payload design and basic parameters of the ground receiver selection, which required in terms of the impact of nonlinear effect, and make compromise between efficiency and distortion. This paper studies these two issues, the main research content and contribution are as follows:1. Analysis of the interference between the GNSS signals. The paper set up SNIR analysis model and code tracking error analysis model, derived the analytic expression of SNIR and the analytic expression of code tracking error standard deviation, use the code tracking error standard deviation and the equivalent carrier to noise ratio which derived from SNIR to characterized the quality of GNSS signals. And made the definition of the interference coefficient and the code tracking interference coefficient, the two coefficients only take into account the signals central frequencies and theirs waveforms contributions to the interference, shield the effect of power. So at the initial stage of signal designing, these two coefficients can be used for preliminary assessment the impact of interference signal on the target signal, the coefficient is smaller, the impact is smaller.2. Proposed the code tracking error increment as one of GNSS radio frequency compatible assessment parameters. At present, some of the literature use the degradation of carrier to noise ratio as GNSS radio frequency compatible assessment parameter, this parameter reflects the interference on the impact of the signal carrier to noise ratio, but does not reflect the interference on the impact of the tracking code, in order to measure the code tracking error caused by the intrasystem interference and intersystem interference, we proposed the code tracking error increment.3. Based on previous theoretical analysis, gave the assessment methods and steps of intrasystem radio frequency compatibility and intersystem radio frequency compatibility.4. The GNSS baseband signal power spectrumthe within pre-calculated integral time is required, when assessing GNSS radio frequency compatibility and analysis of receiver coherent processing. At present, the impact of the length of pre-integral time on the base-band navigation signal spectrum structure is not be concerned, aim at this problem, the GNSS baseband signal power spectrum within pre-integration time under both cases is derived in this paper. The first situation: pseudo-random code cycle is less than or equal to pre-integration time; The second situation: pseudo-random code cycle is greater than pre-integration time. The derived power spectral analytic expression can be used to analyze the Gabor bandwidth and code tracking accuracy, as well as pseudo-code on the impact of the signal power spectrum within pre-integration time, to assist analyze the performance of the actual signal after the coherent receive.5. A lot of literature ambiguously use the concept of when calculation interference coefficient, and didn't clearly define conditions using long codes, aim to these problems, we first identified the concept of long codes, the so-called long codes are those navigation signals which power spectrum can be substituted by the chip power spectrum when calculation the interference coefficient and the tracking code interference coefficients. And analyzed the impact of interference coefficient estimation error on the degradation of carrier to noise ratio, based on this analysis, proposed that interference coefficient estimation error is not more than 0.2dB to be the long codes defined indicators, then come to two criteria of defined long codes. Criteria I: As long as navigation signal parameters to meet the pseudo-code cycle greater than or equal to the period of data bits(symbolized T_b), when the frequency difference is greater than 1/T_b, the navigation signal is defined as a long code. Criteria II: When calculating the interference coefficient between the long code and short code, the short code power spectrum can be substituted by chip power spectral.6. Analysis of L1-band GPS intrasystem interference, gave the degradation of carrier to noise ratio and code tracking error increment of C/A code, P(Y) code, M code and the L1C data channel and pilot channel signal respectively. Analysis of Galileo intrasystem interference, gave the degradation of carrier to noise ratio and code tracking error increment of the PRS signal and the OS data channel and pilot channel signal respectively. Analysis of interference between GPS and Galileo signal, and gave the degradation of carrier to noise ratio and code tracking error increment of all signals respectively. The simulation results show that, GPS intrasystem interference is more serious than Galileo intrasystem interference, and Galileo suffer interference from GPS is large than GPS suffer interference from Galileo.7. As the high-power amplifier nonlinear effect, the limited bandwidth of the navigation signal distortion increase, which would affect navigation signals in the power spectrum, and pseudo-code tracking accuracy. To address this issue, the thesis established the generic model for analyzing navigation signals non-linear distortion, used out-of-band power loss, the correlation loss and the offset of zero-crossing of S-Curve to assess the impact on navigation system performance, and analyzed how the bandwidth restrictions and nonlinear effects impacted on Rectangular pulse shaped, SRC(Square Root cosine) pulse shaped, BPSK modulation and BOC modulation.
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