Field Distribution Characteristics of Leaky-Wave System in the Vacuum Tube for High-Speed Rail

The vacuum tube high-speed rail is a new type of rail transportation technology. The maglev train is running in the low-pressure tube close to vacuum, with ultra-high speed, all-weather, no wheel-rail resistance, low air resistance and low noise mode. The vehicle-to-ground wireless communication system is the key to the safe operation of vacuum pipeline ultra-high speed rail. Wireless free-wave method used in the traditional high-speed rail antenna system is not suitable for the vacuum tube ultra-high speed train environment, because the Doppler effect will become extremely obvious which is bad for communication. Therefore, in this paper the solution of leaky-wave system is selected to effectively suppress the Doppler effect in the vacuum tube. The leaky waveguide can be conveniently fabricated and integrated together with the tube, and the operating frequency is chosen at 3.3 GHz for the 5G communication. The simulation results show that cylindrical waves can be radiated by the leaky waveguide, and uniform phase distribution can be achieved along the rail direction, which can eliminate the Doppler effect when the ultra-high speed train is running. It is also found that the higher-order harmonics are mostly confined in the near region of the leaky-waveguide. The field distribution becomes flatter when the observation point is away from the leaky-wave system.