| The vortex electromagnetic wave with orbital angular momentum(OAM)has infinite orthogonal eigenmodes in theory,and hence it has the potential to improve the communication capacity and spectrum utilization,which has gradually become a research hotspot of scholars at home and abroad.Using the unique advantages of metasurface for phase modulation,in this paper,the research of vortex wave antennas is carried out.The main research contents and innovations are summarized as follows:(1)The design method of single-beam and single-mode OAM vortex wave antenna is proposed.A reflective metasurface-based antenna with 50 cm × 50 cm is designed by using spilt-ring elements.The simulation results show that vortex wave with l=+1 is successfully generated by the designed antenna,and the OAM bandwidth of 33.3%and 1-dB gain bandwidth of 23%are also achieved.Based on the transmission line matching theory,a Jerusalem cross slot element is proposed,which can realize 360°transmission phase range with transmission magnitude greater than-0.45 dB.Based on the proposed element,a transmissive metasurface-based antenna is designed.The simulation results show that vortex wave with l=+1 is successfully generated by the designed antenna,and the maximum aperture efficiency of 11.3%is also achieved.(2)To solve the problem of single-beam and single-mode OAM vortex wave antenna with single mode and narrow coverage,a design method of multi-beam and multi-mode OAM vortex waves antenna is proposed.A wideband dual-beam and dual-mode OAM vortex waves antenna with 75 cm × 75 cm is designed by using dual-semi-split-loop elements.The measured results show that two vortex beams with different OAM modes are successfully generated,one beam is toward the direction of(20°,0°)with OAM mode of l=+1,whereas another beam is toward the direction of(20°,180°)with an opposite OAM mode of l=-1.And the OAM bandwidth of 50%and 1-dB gain bandwidth of 33.3%are also achieved.A reflective element loaded with a micromotor is proposed,which can realize a 360° continuous reflected phase shift with adjustable electronic control.Based on the proposed element,a reconfigurable OAM vortex waves antenna with 25 cm × 25 cm is designed,which can produce vortex waves with different OAM modes in different directions.(3)In view of the serious divergence effect of OAM vortex wave in microwave transmission,a design method of non-diffractive OAM vortex wave antenna is proposed.A wideband high-order Bessel non-diffractive OAM vortex wave antenna with 75 cm × 75 cm is designed by using multi-ring-cascaded elements.The measured results show that high-order Bessel beam with l=+1 is successfully generated by the designed antenna,and the OAM bandwidth of 50%is also achieved.Compared with vortex beam,the high-order Bessel beam with the same OAM mode generated by the designed antenna has smaller divergence characteristic in the near-field transmission. |
PDF Full Text Request