Radiation Characteristics Of Rectangular Leaky Waveguide Under High Speed Railway Environments

In high speed railway or urban transportation systems, the maintenance of a real time, high-speed and high-quality broadband train-to-wayside communication at all locations along the track poses a major problem. Because of the social economic development, the reality demand for improving the operation speed of the train exists. At the period of rapid development of mobile technologies, such as3G (3rd-generation) and3.5G, people are constantly seeking for the ways to use those communication technologies to achieve higher transmission rate. Among them, a communication frequency range of2-6GHz is widely in use, which is based on WiFi and WiMax mobile protocol standards. Based on these bands, there are many kinds of wireless coverage networks in high speed railway communication system, such as wireless station, coaxial cable leakage. The communication through a rectangular leaky waveguide, based on two-hop vehicle-to-ground structure that is continuously laid along the track is used. Over the required communication ranges of several hundred meters between stations, such waveguides provide low longitudinal attenuation and has several advantages over other wireless networks..At present, the rectangular leaky waveguide has already been used in some high speed railways, but the development is still not perfect. In practical applications, under high speed railway systems, external environment has certain influence on the transmission reliability of leaky rectangular waveguide such as snow accumulation, soil covering, etc. This thesis is mainly about the theory analysis and simulations of the rectangular leaky waveguide that is currently applied in high speed railways and aimed to study its radiation characteristics, operation principles and working modes.The main research and innovations contents:1. According to the operation principles of rectangular leaky waveguide, magnetic current equivalent principle and Love’s field equivalence principle are applied to the analysis of rectangular leaky waveguide, and corresponding radiation field equations are also predicted, which simplifies the calculation. By using those methods as the basis and the approaches, a new leakage waveguide is designed.2. Under the typical environment when the snow covering on the waveguide, theory analysis and simulation for radiation characteristics and transmission characteristics of rectangular leaky waveguide had been researched in this thesis. The influence on the electromagnetic wave radiation by the snow as a conductive medium has been summed up. The theoretical basis is proposed for the future design of more suitable leakage waveguide with different slots positions or different operation frequencies.3. A set of suitable radiation analysis method and flow are summed up for different types, different length and different environments of the rectangular leaky waveguide in this thesis, which provides an important basis for suitable waveguide choosing, installation and designing.