| With the rapid development of modern wireless communications,requirements for antennas are increasing day by day.The Fabry-Perot(F-P)resonator cavity antenna has received extensive attention from people because of its simple structure and high gain.As a special scatterer for communication and radar systems,the antenna on the stealth platform greatly improves the RCS(Radar Cross Section)of the entire system.While realizing the low RCS of the antenna,how to maintain or even further improve the performance such as the bandwidth and aperture efficiency of the antenna will be of great significance.In addition,as a new type of array antenna,the reflectarray antenna has high gain and manufacturing flexibility,and it is widely used in satellite communications,radar detection and other fields.Because the reflectarray antenna based on the polarization conversion metasurface has a simple structure and can be applied to the design of reconfigurable reflectarray antenna,so it has great research value.In this paper,a broadband reflectarray antenna is designed based on the polarization conversion metasurface.Besides,the orbital angular momentum technology can greatly increase the communication capacity and is expected to solve the problem of scarcity of spectrum resources.At the same time,the divergence angle of the OAM vortex wave is closely related to the transmission distance,and the low divergence angle OAM antenna has broad application prospects in long-distance transmission.In this paper,two Fabry-perot resonator antennas are designed based on orbital angular momentum technology.The main research contents of this paper are as follows:1.A broadband and high aperture efficiency Fabry-Perot resonator cavity antenna with low RCS based on nonuniform superstrate is designed.Among them,the superstrate consists of four kinds of FSS units which are arranged in a configuration of four concentric square frames.Because the reflection phase difference of the upper surface of the four FSS units is maintained at nearly 90° in turn within the working frequency band,the antenna realizes a broadband RCS reduction.At the same time,because the lower surface of the superstrate,that is,partially reflecting surface(PRS),has the characteristic that the reflection phase changes with the positive slope of the frequency and the characteristic that the reflection amplitude decreases from the center of the superstrate to the edge,the antenna realizes a wider 3-d B gain bandwidth and higher aperture efficiency respectively.The measured results show that the designed antenna has a wider 3-d B gain bandwidth,high aperture efficiency and low RCS.2.A wideband reflectarray antenna based on polarization conversation metasurface is designed.A 2-bit phase shifter is proposed based on the polarization conversation metasurface unit cells,which achieves a phase shift of 0°,90°,180° and 270° in a wide frequency band.Based on this polarization rotating unit cell,a reflectarray antenna is designed.The measured results show that the antenna achieves a maximum gain of 25.6 d Bi at 13.2 GHz and an aperture efficiency of 35%,with a 1-d B gain bandwidth of 30.4% and a3-d B gain bandwidth of 41.4%.3.Two kinds of Fabry-Perot resonator cavity antennas are designed to realize the low divergence angle of OAM vortex beams.By designing the feed network,both slot array antennas and patch array antennas can generate OAM vortex beams with a mode of-1.At the same time,by loading the Fabry-Perot resonant cavity,two OAM antenna arrays can achieve divergence angle reduction and gain enhancement. |
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