Research And Analysis On Disturbance Characteristics Of TD-LTE’s Radiation Emitted In High-speed Rail

With the rapid development of high-speed railway, digital communication system for railway is required higher on the reliability and safety for railway transport. As the second generation mobile communication technology, GSM-R belongs to a narrowband communication system, which has low spectral efficiency and data rates, and it is difficult to meet the needs of new business. As the most advanced communication system, TD-LTE uses orthogonal frequency division multiplexing and multiple-input multiple-output technology, which greatly enhances the spectral efficiency and data rates. International Union of Railways has identified LTE technology as the next generation railway mobile communication network. However, the technical standards of LTE-R are in the research stage.Due to the extremely complex electromagnetic environment of the high-speed rail, the interference of electromagnetic radiation is likely to cause reduction of speech quality and data transmission error in wireless communication. If the TD-LTE communication system is used in high-speed railway, it is very necessary to research reliability and electromagnetic compatibility features of the TD-LTE. Relying on the "next-generation broadband wireless mobile communication network," National Science and Technology Major Project of MIIT:"The key technology research and verification of high-speed railway broadband communications based on TD-LTE", this paper mainly studies and analyzes the radiation emitted disturbance characteristics of TD-LTE.The work and innovations of this paper are listed as follows:Firstly, based on technical characteristics of TD-LTE communication system, OFDM signal and subcarriers suppression after adding cyclic prefix are simulated and analyzed. The Gaussian pulse are received as the excitation source of antenna through approximation by time-domain OFDM signal.Secondly, the method of radiation emitted test and simulation analysis are studied. First of all, through theoretical calculation, the radiation field intensity of LTE signal as dipole antenna’s excitation is received. Then using finite integral method (FIT), the far field characteristics of LTE signal launched by dipole antenna is analyzed. And this thesis obtains the band leak influence of LTE-R and mutual interference with GSM-R. Compared with theory and simulation, this thesis conclude that the external leakage field in the900MHz band produced by LTE-R is not enough to harass on GSM-R.Thirdly, based on MIMO antenna technology principles, a2×2MIMO meander line antenna is designed. And optimize the antenna so that the isolation of the two antennas is above10dB. Furthermore, the far-field disturbance characteristics of the antenna are analyzed through loading LTE signal. And the conclusion is that the leakage harass of LTE signal launched by multiple antenna is smaller than that launched by single antenna.The research results of this article provide theory basis for the subsequent actual tests of TD-LTE’s radiation harassment in high-speed railway. And it will lay a solid foundation for research and standard of next generation mobile communication system for railway.