| Among the high-gain antennas,the metasurface lens antenna has many advantages,such as small size,light weight and easy to manufacture,and no feed resistance plug,which is very suitable for 24 GHz radar application systems.The metasurface lens antenna can be regarded as consisting of a feed antenna and a metasurface lens.The performance of the metasurface lens has a major influence on the overall lens antenna.Therefore,the research and design of the metasurface lens have attracted the attention of scholars and researchers.In this paper,the metal metasurface lens antenna,dielectric metasurface lens antenna and metal-dielectric combined metasurface lens antenna are studied.The main research parameters include the loss of the metasurface lens,the thickness of the lens and the bandwidth,gain,efficiency,and total thickness of the antenna of the metasurface lens.The main work and results of the paper are as follows:1)Based on the resonance characteristics of metal metasurface elements,a low-cost phase gradient metasurface 24 GHz lens antenna based on FR4 dielectric substrate was proposed.In order to achieve a three-layer metasurface structure with a phase shift range greater than 360?,two types of metasurface elements with complementary transmission phases are designed.The structures of these two types of metasurface elements are similar,achieving a total phase shift range of 398?,and the phase linearity is good.All the corners of all units are cut by 1/4 round holes to reduce transmission loss,so that most units with different phase shift control parameters have a transmission coefficient greater than 0.8.Using this complementary unit group,a focusing metasurface with a size of 77mm×77mm was designed,and the lens thickness was 4.762 mm.Combining with a patch antenna as a feed to form the final lens antenna.The simulation and measurement results show that the peak gain of the lens antenna can reach 20.5d B,which is 12.4d B higher than the feed patch antenna.The 1d B gain bandwidth is about 4.8%(1.15GHz),the radiation efficiency is 83.6%,and the aperture efficiency is26.1%,the front-to-back ratios of E-plane and H are 18.5d B and 17.2d B,respectively.The overall performance is good,and it can be used in 24 GHz radar application systems.2)Taking advantage of the low-loss,ultra-broadband,and high-efficiency advantages of the dielectric metasurface unit,an ultra-low profile 24 GHz dielectric metasurface lens antenna based on 3D printing technology was designed.The highest gain is 21.7d B,which is 13.6 d B higher than the feed patch antenna,the aperture efficiency is 33.7%(7.6%higher than the metal metasurface lens antenna),and the 1 d B gain bandwidth is about 15.83%(3.8GHz),which is significantly higher than the metal metasurface lens antenna gain bandwidth,indicating that the dielectric metasurface lens antenna has high gain characteristics of bandwidth.The size of the final lens antenna is 76.5mm×76.5mm×35.9mm.The total thickness of the antenna is smaller than that of metal metasurface lens antennas,and the antenna performance is good.It can be manufactured by mature 3D printing technology,the process is simple and inexpensive,and it can meet the application of 24 GHz radar antenna index.3)Combining the resonance characteristics of metal metasurface units with the advantages of good control of phase and the advantages of low loss,ultra-wideband,and high efficiency of dielectric metasurface units,the third work is a low-profile hybrid 24 GHz metasurface lens antenna which is based on metal structure and 3D printing dielectric structure.In order to reduce the high loss caused by the metal part,a similar unit group with complementary transmission phase is designed to reduce the number of layers of the metal part by using the idea of ??the complementary transmission phase of the unit group in Chapter 2.The two types of units in the unit group are composed of a metal part and a dielectric part.The metal part is only designed on a double-sided copper-clad board.The dielectric part is composed of a simple dielectric column.The two parts of the structure control the transmission phase together,achieving a total phase shift range of420?(significantly more than 360? phase shift coverage requirements),andphase shift linearity is good.The size of the final lens antenna is65mm×65mm×31.4mm,and the maximum thickness of the metasurface lens is 8mm(where the thickness of the metal part is 1.6mm and the thickness of the dielectric part is 6.4mm).Compared with the metal type metasurface lens antenna,the size is reduced.The size of the metasurface lens array reduces the total thickness of the antenna,and also reduces the thickness of the dielectric unit,thereby further reducing costs.The peak gain can reach20.3d B,the aperture efficiency is 33.9%(the highest of the three proposed antennas),and the front-to-back ratio of the xoz and yoz plane are 22.9d B and 19.8d B,respectively.The gain bandwidth of 1d B is about 9.7%(2.32GHz),which is about 5% higher than that of metal metasurface lens antennas.It is proved that adding a dielectric to control the partial phase shift can effectively increase the gain bandwidth.This hybrid structure opens up new approaches and methods for the research and design of metasurface lens antennas. |
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