Wireless access of high speed flying train based on leaky electromagnetic lens

With the rapid development of the high-speed railway in recent years, the transformation of transportation technology is gradually breaking through the shackles. The dense atmosphere is the key factor restricting the development of the wheel-rail high-speed railway. The high-speed vacuum tube flying train is a novel rail technology, which breaks through the restriction of the medium. The maglev train can run at ultra-high-speed (over 1 000 km/h) in the low-pressure metal tube close to the vacuum. As for the vehicle-ground communication, the base stations deployed along the tube can not establish the wireless link with the train inside the tube due to the enclosed tube wall, thus the leaky waveguide is adopted to achieve wireless coverage inside the tube. Through the special slots design of leaky waveguide, the electromagnetic wave radiates in cylindrical waveform form, thus it can effectively restrain the extremely high Doppler frequency shift caused by ultra-high speed. Aiming at the problem of how to realize effective and seamless communication between train and leaky waveguide, this paper proposes an access method, in which an electromagnetic medium lens is installed on the train roof to directly achieve wireless coverage for passeng- ers inside the train. Furthermore, based on the relationship between the medium thickness and phase, the lens thickness is designed to transform cylindrical wave to plane wave, which can converge the propagation direction and improve the antenna gain to achieve more uniform wireless coverage in the train.