Study On Wideband And High-Efficiency Transmitarray Antennas

Transmitarray antenna(TA)is a high-gain antenna that has attracted extensive attention in the field of antennas in recent years.It has the advantages of easy fabrication,low cost and high gain.The traditional transmitarray antenna consists of a feed source and a planar array composed of several transmission elements.Compared with the traditional transmitarray antenna,the folded transmitarray antenna has one more polarized rotating reflection surface,so that the incident wave is transmitted after multiple reflections.This structure reduces the overall profile of the antenna.In this thesis,three different transmitarray antennas are proposed to realize broadband and high-efficiency radiation characteristics.The main contribution of this thesis is summarized as follows.1.A three-layer pure metal broadband high-efficiency transmitarray antenna is designed.The element is composed of three identical metal layers,each of which consists of a square slot and two sets of orthogonal stubs.The element adopts a slot-type pure metal structure,which makes the antenna achieve high gain radiation with low loss.After simulation and optimization,the element can achieve a transmission phase shift of 330° with transmission loss less than 3 d B,and a transmission phase shift of 280° with transmission loss less than 1d B.The bivariate cooperating optimization method is adopted in the element design,and the optimal transmission phase shift curves are obtained.A square transmitarray antenna composed of 144 elements is fabricated.The measured results show that the 1-d B gain bandwidth is 20.5%,and the peak gain is 24.2 d Bi at 12.5 GHz,with a radiation efficiency of 53.5%.2.A double-layer pure metal broadband high-efficiency transmitarray antenna is proposed.The element consists of two pure metal layers and one plated through hole.Each metal layer has four rectangular slots parallel to the diagonal.The element is designed to operate in two states,and the 360° transmission phase shift is obtained by changing the slot lengths of the two states.The low transmission loss and linear transmission phase shift characteristics are achieved by using 45° rotating slots strategy.In order to verify the validity of the design method,a prototype of 332-element transmitarray is fabricated and measured.Measured results show that the transmitarray antenna achieves 1-d B gain bandwidth of 21.1% with peak gain of 28.2 d Bi at 9 GHz and maximum efficiency of 57.6%.3.A broadband high-efficiency folded transmitarray antenna is designed.Different from the traditional folded transmitarray element,the designed element adopts a double-layer metal structure without polarization grid,which further reduces the profile.And the element polarization selectivity is obtained by using the slot-based metal structure.By comparing the performance of the traditional transmitarray and the folded transmitarray with different aperture sizes of the feeds,it is concluded that the small aperture size feed is more suitable for the design of the folded transmitarray.By using the small aperture size feed,the folded transmitarray achieve the 1-d B gain bandwidth of 14.1% and the radiation efficiency of46.6%,and its profile is greatly reduced.