| Bei Dou Navigation Satellite System united with 5G will be promoted and used in a large scale in China,even to the whole world.However,it wasn't considered that the 5G may bring potential interference to Bei Dou during its construction.Since the three signals of Bei Dou L band are close to the frequency interval of 5G band,the Bei Dou signal may be disturbed due to its vulnerability.Therefore,it is necessary to research the impact of 5G signals adjacent to the Bei Dou L band on it.The main contents and research results of this thesis are as follows:1.Bei Dou signal,5G signal frequency band and interface control characteristics are analyzed firstly,then the 5G frequency band that may interfere with Bei Dou system are sorted out.Four potential factors determining the level of interference are given by modeling and analyzing the electromagnetic scene where the Bei Dou signal and 5G signal coexist.The principle of the actual receiver is analyzed to correctly generate the signal of Bei Dou mixed up with 5G out-of-band signal.2.A simulation solution that traversing three parameters of Bei Dou signal mixed up with 5G out-of-band radiation is designed to analysis the relevant law how the four factors impact the final interference level.Simulation results show that the lower power of 5G signal reaching the Bei Dou receiver,the smaller interference generate.And the critical point is around-45 dBW.What's more,the larger frequency interval between 5G signal and Bei Dou signal,the smaller interference generate.The critical point of frequency interval is about90 MHz.Finally,the frequency domain,once the peak of the interference signal located at the main lobe or side lobe of the navigation signal,it would seriously affect the carrier tracking and code tracking respectively.3.The specific interference value of 5G signal to Bei Dou signal is obtained by analyzing all simulation data.When a Bei Dou receiver is nearly closed to a 5G base station and the power of 5G signal arriving the Bei Dou receiver is above-45 d BW,then the standard deviation of carrier tracking error will deteriorate to 1.05 to 1.3 times of the original standard deviation,and the standard deviation of code tracking error will deteriorate to 1.05 to 1.5 times of the original standard deviation.The specific value is determined to the specific power of 5G signal arriving the Bei Dou receiver and the specific frequency interval between Bei Dou signal and 5G signal.4.The transmission power and signal path loss of 5G base station are analyzed,and it is found that the power of 5G signal arriving at the Bei Dou receiver will be below-45 d BW in most scenarios.In this condition,there is no compatibility problem between Bei Dou and 5G.Only in some special scenario where the Bei Dou receiver is too close to the 5G base station with high radiation power,the compatibility problem mentioned in the item 3 would occur.5.Solutions to solve the compatibility problems between Bei Dou and 5G are proposed by analyzing the degradation curve of tracking error labeling.The implementation plan is that5 G base stations whose working frequency band near to the Bei Dou signal should use frequency resources far away from the Bei Dou signal preferentially to reduce the generation of compatibility problems.Using multi-mode and multi-frequency navigation receiver can avoid the decrease of system availability.Lastly,the compatibility problem between Bei Dou signal and 5G signal can be effectively solved by using anti-interference measures in spatial domain based on the difference of spatial distribution.6.The power spectral density of 5G out-of-band radiation is calculated and compared with the existing ITU protection standard.It is found that 5G out-of-band radiation still cause some interference to Bei Dou B1 signal even if it is less than the maximum limit of total power spectral density of broadband interference signal specified by ITU for protecting navigation signal. |
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