| The full opening of beidou-3 satellite navigation system marks that Beidou has entered a new era of global services.However,due to the weak landing power of Beidou signal,it is easy to be interfered by the ground signal,especially 5G signals scattered around the Beidou signal frequency band.Therefore,it is of great significance to study the compatibility between Beidou signals and 5G signals near the frequency band of Beidou signal.This paper takes the regional short message signal of Beidou S-band and the B1 C signal of Beidou Lband as the research target,and focuses on the impact of 5G signals near the B1 C signal and the short message signal frequency band on the capture and tracking of B1 C and short message signals.The main contents of this paper are as follows:1.The BOC and QMBOC modulation methods adopted by the Beidou B1 C signal are introduced,and the correlation,power spectrum and other characteristics of BOC are simulated and analyzed.In addition,based on the Beidou signal system,the structure and composition of the B1 C signal and the power distribution of each component are emphatically introduced.Furthermore,the principle of Beidou parallel code phase acquisition is introduced in detail,and the acquisition process when interference exists;then the principles of carrier tracking and code tracking of the tracking loop are discussed,and the EML code tracking method is analyzed.2.Then,according to 3GPP R15 standard,the frequency band distribution and bandwidth configuration of 5G signal are determined.Through the analysis of 5G time-domain waveform signal and corresponding spectral characteristics,it is known that CP-OFDM has the most serious out of band leakage.In addition,the power limit of 5G signal base station,the out of band and spurious range of 5G signal and their power limits are determined according to 3GPP protocol.Based on the ITU-R M.2412 standard,the lineof-sight transmission(LOS)and non-line-of-sight transmission(NLOS)models of 5G signals in UMa and RMa scenarios and 5G multipath models are simulated and analyzed,which provide a reference for the subsequent determination of the influence range of 5G signals.Moreover,the types of interference(out-of-band,spurious,and third-order intermodulation)of the 5G signal to the Beidou signal are analyzed and calculated,and the results show that 5G out-of-band leakage is the main interference factor.3.The concept of equivalent carrier-to-noise ratio and spectral separation coefficient is derived through the signal-to-interference-to-noise ratio,and then the limitations of the equivalent carrier-to-noise ratio are pointed out.Thus,the interference signal ratio ISR is used to express the influence of interference on the Beidou signal.In addition,according to the definition of the attenuation of carrier-to-noise ratio,it is proposed that the decrease of tracking error before and after interference can be used as an auxiliary index of the influence of interference on Beidou signal tracking performance.Based on the above-mentioned theory,simulation and analysis of the influence of 5G signal on the performance of B1 C signal and short message signal capture and tracking are analyzed.The simulation results show that: in the extreme case of the smallest frequency difference,the ISR corresponding to the successful capture of the B1 C signal is about 37 d B,and the ISR greater than 28.8d B will cause the tracking performance of the B1 C signal to decline,or even the tracking failure(ISR greater than 39.3d B).In addition,the analysis of B1 C measured data shows that the currently deployed 5G base stations will not affect B1C;the ISR corresponding to the successful capture of the regional short message signal is11 d B,and the ISR greater than 12.25 d B will cause the short message signal tracking to fail. |
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