Antenna Modeling And Optimization Research Of Rail Traffic Balise Transmission System

The rail traffic includes the main line railways,urban metros and light rails.The train control and operation system ensures the safety of the rail traffic and increases the transportation efficiency.The two critical technologies of the train operation and control system are location and communication between the onboard and the wayside device.As a spot transmission system,the rail traffic balise transmission system is the perfect location solution in the available technologies,which transmits the controlling information related with safety between the train and the wayside.It is indispensable for the train operation and control system.The rail traffic balise transmission system has three particularities,which include the complicated surrounding environment,high speed movement and multi-antenna inside.As the system works in the complicated outdoor environment,the metal and medium besides the system would shift the resonant frequency of the system antenna,which influences its normal work.When the train with the onboard antenna unit passes the balise,the effect from the balise to the onboard antenna unit is changed with the distance alteration.Simultaneously,due to the balise has tele-powering receiving antenna,uplink transmitting antenna and programming receiving antenna,the mutual coupling among multi-antenna would influence each other.This paper has built the antenna model for rail traffic balise transmission system based on the electromagnetic field theory and proposed the optimization.The three particularities of the system correspond to single antenna,dual-antenna and multi-antenna respectively.The influence from the surrounding complicated environment to the single antenna,the non-constant characteristic generated by the distance alteration between the onboard antenna unit and the balise,the mutual coupling among the multi-antenna inside the balise and coupling reduction method are researched.The main innovations of the dissertation are as following:(1)The antenna environment sensitivity machanism of the rail traffic balise transmission system is analysed in the complicated application environment.The influence from the medium and metal in the real application environment to the balise transmission system antenna is researched.The resonant frequency shift,the magnetic field distribution are analyzed when the antenna approaches the clear water,concrete bed,steel rail or metal plate respectively.The distance between the antenna and the metal or medium is optimized and the method feasibility to reduce the antenna environment sensitivity is verified.(2)The equivalent circuit model of the tele-powering transmitting antenna and receving antenna are built based on the inductance coupling theory and the determinant of the effective communication distance is simulated and analysed.The method to determine the minimum tele-powering is proposed according to the different reflected impedance from the tele-powering receiving antenna to the tele-powering transmitting antenna at different positions.It tunes the both antennas at the beginning of the effective communication distance.The method could ensure the effective communication distance and restrict the maximum tele-powering transmission to protect the balise.(3)The onboard balise programming antenna is proposed and the operation mechanism of the programming antenna is analysed.The results indicate that the programming circuit inside the balise could be activated when the onboard programming transmitting antenna and balise programming receiving antenna adopt 8-shape designing and the vertical distance between the both antennas is 280 mm.The heterogeneous designing between the programming antenna and rectangular tele-powering transmitting antenna is simulated and verified.The results indicate that the programming circuit in the balise is not activated in the non-programming mode,which guarantees the telegram data security.(4)The equivalent multi-port network model of the multi-antenna is built.The mutual coupling among multi-antenna is analysed and the coupling reduction method is proposed based on the infinite element method and infinite integration method.The mutual coupling of multi-antenna increases the loss resistance and decreases the equivalent inductance and self-resonant frequency.It also generates the transferred impedance and shifts the resonant frequency.The influence factors of mutual coupling include the distance between two antennas,the overlap area and the arrangement order of antennas with different operation frequency.In order to reduce the coupling coefficient,the methods are proposed,such as the increasing of distance between antennas,decreasing of the overlap area,rearrangement of antennas with different operation frequency and to add a filter,which decreases the transmission coefficient among antennas below-10 dB and increases the antenna independence.