Design Of VHF/UHF Broadband Vehicle Antenna

The rapid development of in-vehicle communications urgently requires higherperformance in-vehicle antennas.Conventional multi-antenna laterally distributed narrowband antenna systems are difficult to satisfied that requirements.Therefore,in this paper,by analyzing the structural characteristics of the antenna,a new axial combination distribution method and its feed network are studied,and a single-port multi-band broadband vehicle antenna that meets the requirements of the existing vehicle communication is realized.The main research contents are as follows:1.Research on VHF/UHF broadband vehicle antenna.By designing the common structure of the new metal radiating unit,the broadband vehicle antenna is realized.In order to realize the dipole working mode,we disconnected the monopole and coupled the structure in series at the disconnection,and introduced a new feed.Lumped passive matching networks and ferrite chokes are used to make single/dipoles meet the matching requirements of their respective operating bands.The design of a VHF broadband vehicle antenna is completed by using a diplexer to feed power through one port.In order to achieve wider bandwidth,a dipole antenna is axially combined on top of the designed VHF broadband vehicle antenna,and the coaxial feed line of the dipole antenna is conformed with the coupling structure below to reduce the impact from the feed network.Finally,the highperformance lowpass-bandpass-highpass triplexer is used to combine the three ports into one port for feeding,and a VHF/UHF broadband antenna that meets the requirements of vehicle communication is realized.2.UHF vehicle dual-band antenna research.In order to satisfy the requirements of vehicle communication in the UHF frequency band,a sleeve-disk cone axial combined structure antenna with a new feed network was designed,in which the sleeve antenna is responsible for low frequency radiation and the disk cone antenna is responsible for high frequency radiation.The sleeve structure and the base are conformal to improve the mechanical stability of the vehicle antenna.In order to achieve single-port feeding,a lowpass-bandpass broadband diplexer is designed,which uses a lumped-microstrip distributed parameter combination structure to achieve miniaturization,and uses the lowpass filter’s spurious passband to improve cut-off characteristics.In order to reduce the coupling effect caused by the feed network,the coaxial line of the diplexer’s bandpass output port is wound on the ferrite to achieve the high impedance characteristic of the skin to ground.Then,the skin and the lowpass output port of the diplexer are connected to feed the sleeve antenna,and meanwhile,the coaxial wire passes through the sleeve antenna element to feed the cone antenna.Using a diplexer and a single coaxial wire to feed the sleeve antenna and the cone antenna simultaneously,the research and design of the UHF vehicle dual-band antenna is finally realized.