Study On The Technique Of Wideband Metalens Antenna Based On Phase Compensated Metasurfaces

In this thesis,wideband and high gain metalens antennas were researched.The metalens antennas consists a feed source and a metalens.The metalens is constructed by numerous transmit unit cells.Base on the principle of phase compensation,the metalens design methodology,phase and distribution characteristics of metalens unit cells of wideband metalens antenna are studied.The main research contents include:In this thesis,the working principle,theoretical basis and design method of broadband planar metalens antenna are studied.First,the working mechanism of the traditional lens antenna is analyzed.Then,the structural characteristics and discrete phase distribution characteristics of the planar metalens antenna are discussed based on the principle of phase compensation.The generalized Snell's law is studied to explain the generation mechanism of this discrete phase.A broadband metalens antenna prototype in the millimeter wave band is proposed based on phase compensated technique.First,based on the principle of phase compensation,the designed transmission array is divided into 3bit phase regions,and the phase of each region is discussed.Then,using the hybrid multilayers metal structure,8 transmission units with phase coverage of 2? were designed to meet the phase requirements of the broadband array.Then,the location of the unit was optimized and the transmission array,which consists of17×17 units was designed.By loading the designed transmission array on the horn feed,the simulation results show that the designed metalens antenna works in a wide frequency range of 50-79 GHz.In the working frequency band,the transmission array increases the feed gain by 6 d B,and the highest gain is 25.3 d B(71 GHz).The aperture efficiency is 42%,and the3-d B gain bandwidth is 25%.The designed broadband metalens antenna is fabricated and measured,and the gain curve of the antenna in the measured frequency range is basically consistent with the simulation results.The application of the electromagnetic polarization conversion metasurface in the highgain metalens antenna has studied.First,the characteristics of the polarization conversion metasurfaces are researched,then,the principle and analysis method of polarization control are introduced,and the structural characteristics of the linear polarization conversion electromagnetic metasurface unit are analyzed.A reflective linear polarization converter is designed by multilayer structure.The polarization converter realizes a 90° polarization rotation for the y-polarized incident electromagnetic wave.The operating band is 52%,and the polarization conversion ratio is higher than 98%.According to the principle of phase compensation,a metalens antenna with polarization conversion function is designed.The corresponding linear polarization conversion transmission unit is designed according to the phase distribution characteristics of the metalens,and these units are used to form the transmittarray.A patch antenna fed by a waveguide is also designed as the feed source of the metalens.The gain enhancement of the patch antenna reaches 7-9 d B in 57-80 GHz.The result shows that,the gain of the feed antenna is increased by 10 d B within 60-80 GHz,and the radiation pattern of the feed antenna is greatly improved.