Research On EMC Characteristics Of EMU Wireless Network Antenna System

With the continuous development of intelligent railways,EMUs have gradually adopted wireless networks for information transmission,and vehicle-mounted antenna systems will also be widely used in train wireless networks in the future.The performance of the antenna directly affects the quality of wireless transmission,and the transmission path of the antenna will be affected by the interior environment of the train.At the same time,the antenna is also exposed to a complex electromagnetic environment,and the wireless transmission in the vehicle is easily disturbed.Once data transmission failure occurs,it will affect the communication quality of the wireless system.This paper studies the vehicle-mounted antenna design,antenna transmission and antenna system electromagnetic compatibility of the EMU wireless network system,and provides technical reference for the safe and reliable operation of the wireless network on the high-speed EMU.The research content of this paper is as follows:(1)Analyze the wireless transmission theory and the key electrical parameters of the antenna,and further analyze the interference of the interior environment of the EMU and the electromagnetic radiation of the on-board electronic and electrical equipment on the transmission performance of the antenna.(2)Model the vehicle antenna,study the design method of the omnidirectional dipole and directional microstrip patch antenna and the working performance in the 2.4GHz frequency band;innovatively design a single cone with a stepped gradient structure The MIMO vehiclemounted broadband antenna was developed and tested.The results show that all key indicators of the antenna meet the design requirements.(3)Analyze the interior materials of the EMU and the layout of the internal environment,and use the CST electromagnetic simulation software to establish a simulation model for the transmission of the EMU carriage and antenna system;for dipole,patch and self-developed single cone MIMO Antennas,use the built model to calculate the in-vehicle transmission effect of different types of antennas in the 2.4/5.8GHz frequency band,and compare and analyze the simulation data.The results show that the designed single-cone MIMO antenna has better communication performance;The impact of off-line electromagnetic interference of converters and pantograph-catenary on the vehicle-mounted antenna system;the simulation calculation of the same-frequency interference of train passengers’ mobile phones to the wireless system,and the study of antenna transmission under the interference condition.(4)Use MOXA communication equipment and various interior materials to simulate and build the environment inside the train,and set up a wireless network test platform.Using a spectrum analyzer and SignalVu-PC software,test and analyze the power,spectrum mask,spectrum flatness,constellation diagram and EVM qualification of the wireless network transmitting end signal;for the receiving end,test the Client using MOXA omnidirectional antenna,directional antenna and self-developed single-cone MIMO antenna in the 2.4/5.8GHz frequency band transmission effect,and analyze the influence of communication frequency band,antenna type,and obstacle occlusion on the transmission effect.