Research On Wide-band Dipole Antenna Array Based On Tightly Coupled Structure

In recent years,a new type of broadband array antenna technology has been proposed in the field of antenna technology,namely,a broadband array antenna technology based on a tightly coupled structure.It was found that the strong coupling effect between the antenna elements can make the impedance characteristics of the array elements change smoothly when the frequency changes,so that a wider impedance bandwidth can be achieved by simple matching.Adding tightly coupled structures can eliminate the need for additional structures such as decoupling networks to simplify the array structure.In addition,the performance of a tightly coupled antenna array can be further improved by loading the dielectric layer with the frequency selective surface.An ultra-wideband array antenna can be obtained by integrating the dielectric layer loading technology and the frequency selective surface technology.This dissertation focuses on tightly coupled antenna array theory and equivalent circuit theory,and combines media loading method with frequency selection surface to study closely-coupled antennas.The main research work is as follows:Firstly,based on the tightly coupled antenna theory,the influence of the tightly coupled structure on the bandwidth performance of the antenna is analyzed.Taking the tightly coupled dipole antenna unit as an example,the effect of the width and depth of the tightly coupled structure on the bandwidth of the antenna is analyzed,and the effectiveness of the tightly coupled structure to widen the bandwidth of the antenna is verified by comparing with the dipole antenna;the above analysis results are taken as reference Based on tightly coupled antenna theory,a compact,compact,tightly-coupled antenna with a maximum size of 20 mm is designed to cover the frequency band from 1.2 to 4.0GHz and 6 to 7.6GHz.Secondly,the effectiveness of the media loading and frequency-selective surfaces in broadening the bandwidth of tightly coupled antennas was investigated.The square ring resistance type frequency selective surface is used to effectively suppress the influence of the ground plate,and a resistive type frequency selective surface is designed by an equivalent circuit method.The validity of bandwidth widening of tightly coupled antennas after RFSS loading is verified by an example.The designed RFSS effectively suppresses the floor reflection,so that the antenna radiation performance in the 4.2~6GHz frequency range is greatly improved,thereby increasing the impedance bandwidth of the antenna.Finally,the antenna unit can cover 0.8~7.6 when the VSWR is less than 2GHz.Finally,using the tightly-coupled antenna designed above as a unit antenna of the array antenna,a 1×4 tightly-coupled antenna array is designed and the VSWR results of each unit are given.At the same time,a metal plate placed at a certain height on the outside of the edge unit is used as an ideal electric wall to improve the impedance matching performance of the edge unit and the truncation processing method is used to cut the array,and the comparison results before and after are given.The operating frequency range of VSWR less than 2 before the truncation process is 1.6~6.5GHz,and the working frequency range of VSWR less than 2 after the truncation method is used is 0.8~7.3GHz.