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.