The Research On Mutual Coupling Effects Caused By The Layout Of The Antennas On Locomotive

High-speed passenger transportation is the common trend of world's railway development. EMU is providing us the fast and comfortable way to travel.At the same time the security issue in high-speed running state has been a topic concerned by people for a long time. Besides the existing 450MHz radio and GPS vehicle satellite positioning system, the CTCS-3 level Train Control System whose core is the GSM-R wireless communication system has been applied to the lcomotive. There must be multiple antennas coexisting on the top of locomotive. Because of coupling, there is electromagnetic interference among Antennas. If we do not solve the coupling problem of antennas, the proper work of the locomotive system may be impacted. What is more, there will be serious hidden danger in road safety. Vehicle antenna works in the open but very finite space environment, the usual spatial isolation and shielding techniques cannot be used to restrain antenna interference, and a reasonable layout of the antenna is the effective way to reduce the mutual coupling between antennas.In this paper, combining the previous research about antenna systems of vehicle and aeroplane recently, a simple antenna system model has been set up first. That is a system composed of a finite and metallic rectangle which is multiple antennas laid on. Then linking the effect between the antenna performance and actual circumstance on the top of locomotive, refine the model. Thinking over the influence of the obstacle and using the coupling as the optimized parameters, the objective function has been proposed. Based on Matlab high-level language, the optimized layout of locomotive antennas has been given by genetic algorithms. It provides a theoretical guidance for the actual layout of the locomotive antennas.Furthermore, the hybrid of high-frequency-computing way and method of moments has been used to simulate the antenna on the locomotive roof. Concretely analyses including how the body,edge effects,barrier bloc,catenary,ground and other factors impact the antenna performance. A large number of coupling simulations have been carried out which is about the anteriorly optimized and optimized layout of the antennas. And it verifies the genetic algorithm is a correct and effective way to optimize the layout of antennas.Finally, an experiment has been done in the semi-anechoic chamber. Ignoring the real impact of the ground and the body, the total reflection surface roof has been considered as the top of locomotive and the surround is free space. Considering the obstacle or not,a lot of useful data have been got after testing the coupling of "line" glyph and the "W" shape layout of the antennas by vector network analyzer. And comparing the theoretical results and the data obtained from the experiment, error analysis is given.