The optimization study of the on-board antenna of BTM based on electromagnetic model

When the speed of the train is 350km/h, it only takes about 7ms for the on-board antenna of BTM to pass the effective range of a balise. On-board antenna needs to accomplish a communication with balise within such a little time that it is essential for on-board antenna to have a good performance of transmitting and receiving signal. Therefore, it is significant to study the optimization of the performance of on-board antenna. This paper presents a method of optimization study about on-board antenna of BTM based on electromagnetic model. Firstly, theoretically analyse the effects that antenna's size, the conductor's diameter and form have on the Gain, Efficiency and near field of the antenna. Then design a square tubular on-board antenna of BTM, which frequency is at 27.095MHZ, and ascertain the optimal conductor's diameter of the on-board antenna; secondly, simulate and model the on-board antenna with FEKO software; thirdly, optimize the size of the established antenna model by OPTFEKO with particle swarm optimization (PSO) algorithm to ascertain the optimal size of the on-board antenna. The results show that the near field radiation of the optimized on-board antenna is much higher and steadier in effective range, and quicker weakening in side lobe zone, when compared with rectangle laminated antenna. The study of on-board antenna optimization in this paper is a good foundation for further study of transmission performance of balise system.