Research And Design Of Low-profile Antenna For V2X

In recent years,the increasing number of cars has led to traffic congestion and traffic accidents,which impeded urban development.Dedicated short-range communication（DSRC）technology is the crucial technology to achieve autonomous driving.In addition,the V2X（vehicle to everything）communication system dominates the transmission and reception of vehicle information.The latest research on vehicle antennas mainly focuses on low profile,wide frequency band,high gain,and multi-frequency.The low profile provides the reduction of wind resistance during driving and plays a role in beauty and concealment.Broadband characteristics can ameliorate the channel capacity of the antenna.High gain characteristics can improve communication coverage.Multi-frequency characteristics can bring the versatility of the antenna.Therefore,low-profile vehicle antenna with broadband,multiple frequency bands,and high gain are designed and studied based on V2X.The specific content of the thesis is as follows:1)A low-profile broadband omnidirectional antenna working in the DSRC frequency band is designed.By loading a coupling ring outside the center-fed circular patch,loading four rectangular ring slots on the ground plate,and symmetrically loading six stubs on the outer edge of the ring,three resonance modes are generated,and therefore the working bandwidth of the antenna is widened.The measured results show that the impedance bandwidth of the antenna reaches 17.6%（5.54-6.61GHz）.The antenna height is only 0.032λ₀（λ₀is the wavelength corresponding to 5.9GHz）.The maximum gain is 3d Bi.The antenna has vertical polarization characteristics,and the horizontal direction is omnidirectional radiation.2)A high-gain omnidirectional antenna working in the DSRC frequency band is designed.A snowflake-like structure with metamaterial properties is proposed.The circular array composed of the structure is loaded around the reference omnidirectional antenna to change the electromagnetic wave transmission path to achieve high gain.The measured results show that the maximum radiation angle gain at 5.9GHz is increased by approximately1.5d B,and the horizontal plane gain is increased by about 0.6d B.The horizontal plane gain can be further increased by loading six slotted sector rings between the circular patch and the snowflake array.The measured results show that the gain in the horizontal plane can reach 1.2d Bi at 5.9GHz.Compared with the reference antenna,the horizontal plane gain is increased by 3.4d B.3)A low-profile antenna integrating GPS,WLAN,and DSRC is designed.The antenna adopts a multi-layer stack structure.The bandwidth of the DSRC and WLAN frequency bands are respectively expanded by loading the coupling ring and short-circuit pins.The isolation between the ports is improved by inserting a third-order Butterworth low-pass filter on the GPS coaxial feeder.The simulation and measurement results show that the antenna has the characteristics of right-handed circular polarization,omnidirectional vertical polarization,and omnidirectional vertical polarization in the GPS,WLAN,and DSRC,respectively.The isolation between the two ports is more than 17d B.In addition,the designed antenna has a low profile of 4.8mm.Moreover,the maximum gains in the three frequency bands of GPS,WLAN and DSRC have reached 3.5d Bi,1.3d Bi,2.3d Bi,respectively,achieving higher gains.