Research And Design Of Omnidirectional Vehicle Array Antenna

Although omnidirectional antenna has been widely used in vehicle communication system,the increasingly complex electromagnetic environment puts forward new application requirements for vehicle antenna,that is,while having omnidirectional radiation characteristics,it is also necessary to achieve its broadband miniaturization.In this paper,based on the actual engineering requirements,with omnidirectional antennas and broadband array antennas as the targets,we mainly focus on the broadband technology of tightly coupled structure antennas and sleeve antennas,and design two broadband array antennas with good performance.The main contents are as follows:1?Design of planar dipole array antenna based on tightly coupled structure.First,based on the basic principle of the tightly coupled structure,add a parasitic structure between the elements of the traditional dipole array antenna to form a tight coupling structure with the adjacent vibrator arm.Then through the simulation analysis of the length and spacing of the coupled structure,the influence of the tightly coupled structure on the impedance characteristics of the antenna is verified.Secondly,the equivalent circuit of the tightly coupled structure is discussed,and it is verified again that the tightly coupled structure can improve the impedance matching of the antenna and widen the bandwidth by changing the impedance characteristics of the antenna.Finally,a planar dipole array antenna based on a tightly coupled structure is proposed.The antenna consists of two dipoles,a tightly coupled structure,a parasitic structure at the feeding point and a feeding network.By adjusting the parasitic structure and tight coupling structure to improve the impedance characteristic of the antenna,so as to achieve a good impedance matching of the antenna within a wide operating bandwidth,and reduce the standing wave of the antenna.The simulation and measured data show that the antenna has a VSWR ?2.5 in the working frequency band of 500-2200 MHz,and the gain in the horizontal direction is above 0d B.2?Design of asymmetric dipole array antenna based on sleeve loading.Based on the theory of the sleeve antenna,a sleeve antenna loaded with a short-circuited metal ring was proposed.The antenna consists of two asymmetric dipoles,a tight coupling structure and metal sleeves.It is mainly based on the wide-band characteristics of tightly coupled array antennas,at the same time,the sleeve structure is added on both sides of the feed port to change the current distribution on the vibrator arm,so as to improve the radiation characteristics of the antenna.Then,by adjusting the length of the sleeve and the way of loading a short-circuit metal ring to achieve the design requirements for antennas with VSWR ?2.5 in the 225-800 MHz band.The simulation and measured data show that the antenna has good horizontal omnidirectional radiation characteristics while having more than three frequency-doubling bandwidths.