Design And Research Of Orbital Angular Momentum Plane Reflectarray Antenna

With the rapid development of communication technologies,the ever-increasing communication services have made the non-renewable spectrum resources increasingly scarce.In recent years,the information modulation capability exhibited by the electromagnetic vortex wavefront form has attracted more and more attention at home and abroad.Theoretically,there are an infinite number of modes and good orthogonalities between different modes for vortex electromagnetic wave.Applying the orbital angular momentum theory to the field of wireless communication,different signals can be transmitted on the same frequency without interference simultaneously based on the different modes,which greatly improving spectrum utilization and communication system capacity and providing a completely new solution of the multiplexing technology for the field of wireless communication.Reflectarray antennas has a large number of the phase-shift characteristic units,which can change the surface phase distribution of the reflectarray to achieve beamforming by adjusting the structural parameters.Therefore,it is very suitable for generating OAM beams with high gain and small divergence angle.In this paper,some existing technologies of antenna,such as multi-frequency technology,polarization technology,etc.,are combined with OAM technology to generate different OAM modes,which not only further enhances the freedom of OAM antenna design,but also enhances the flexibility of the antenna in practical applications.Firstly,the basic theory of OAM and the generation and detection methods of OAM mode are introduced.Secondly,the calculation formula of the phase compensation of the OAM planar reflectarray antenna is theoretically deduced,and the correctness of the formula is verified,which provides a theoretical basis for the design of the OAM planar reflectarray antenna.Aiming at the problem of the traditional single-resonance structural unit has a large gradient of the reflective phase-shift characteristic curve,and unit does not have enough phase shift range,a unit cell based on sub-wavelength multi-resonant structure technology is proposed,which has good reflection phase-shift characteristics.Then,based on the broadband unit,a broadband OAM planar reflective array antenna operating in the Xband is designed.Finally,the phase and amplitude distribution of the designed reflectarray antenna are simulated and fabricated,and the generated OAM mode is analyzed.A dual-beam multi-polarized OAM reflectarray antenna with dual-mode at a center frequency of 12.5GHz is designed based on multi-beam radiation and polarization control theory.The designed antenna can generate OAM beams with mode numbers of l(28)1and l(28)-1in two different directions.Meanwhile,by changing the incident direction of the feeder,the linearly polarized incident waves can be reflected to form linearly polarized waves and circularly polarized waves.Finally,the phase and amplitude distribution of the OAM beam radiation of the reflectarray antenna is simulated and tested,and the generated OAM mode is analyzed.Firstly,a dual-frequency linearly polarized stacked dipole unit is designed.Then,a dual-band dual-mode multi-polarized OAM planar reflectarray antenna is proposed based on the designed unit which is staggered and arrayed,the reflectarray can generate OAM beams with modesl(28)2andl(28)1at frequencies of 9.5GHz and 18.5GHz respectively.Due to the arrangement of units,the designed reflectarray antenna also has a variable polarization function.Finally,the antenna was simulated and processed.