Research And Design Of Antenna Based On Multimode Vortex Electromagnetic Wave

The electromagnetic wave carrying Orbital angular momentum(OAM)is a kind of electromagnetic wave with a special helical wavefront structure,namely,vortex electromagnetic wave.The mode of vortex electromagnetic wave is represented by orbital angular momentum.With the transformation of orbital angular momentum,vortex electromagnetic wave has an infinite number of modes in the theoretical dimension.Then,due to the orthogonality of each mode,multi-mode vortex electromagnetic wave,as a new multiplexing technology in recent years,is of great significance to solve the problems of low spectrum utilization rate and low communication capacity of wireless communication,and is a hot research content of scholars at home and abroad.Therefore,the study of multi-mode vortex electromagnetic wave has high academic value and significance.This dissertation mainly studies and explores a variety of antennas that generate multi-mode vortex electromagnetic wave.The main research contents and innovations are as follows:1.In view of the narrow bandwidth of the traditional multi-mode vortex electromagnetic microstrip array and the large volume of the array antenna generating the multi-mode vortex electromagnetic wave,a four-feed high-gain patch antenna is designed.Two 3dB coupler is used as the feed network to feed from four feeding points.Compared with single and double feed network,more stable and symmetrical current distribution can be obtained.The gain can reach 9.5dBic,and the vortex electromagnetic wave l=±2 can be generated in the millimeter wave band.2.Aiming at the narrow-band problem of the traditional multi-mode vortex electromagnetic wave array antenna,a wideband multi-beam and multi-mode vortex reflectarray is designed.By using the honeycomb hexagonal open ring element design,the element achieves the broadband performance of multi-resonance,and the bandwidth of the element reaches 83.55%(17.7-43.1 GHz).The reflectarray can generate two beams carrying l=±1 respectively,which beam direction is(20°,0°)and(20°,180°)The OAM bandwidth reaches 68.75%,and the OAM bandwidth reaches 68.75%,covering 21-43 GHz,and the OAM purity reaches 90%.3.Aiming at the problem that the vortex electromagnetic wave beam seriously diffuses with the increase of transmission distance,a wideband diffractive multi-mode reflectarray is designed.The element adopts the embedded double-open ring type to obtain the multi-resonance performance,and the element bandwidth reaches 77.36%(18.5-41.84 GHz).The beam width of the reflectarray is 7.9λ less than traditional reflectarray,and the divergence angle of the vortex beam is effectively reduced.Under the premise of keeping the divergence angle small,the wideband of multimode OAM(l=±1)achieves 36.16%,and the bandwidth covers 29-41.8 GHz.4.Aiming at the problem that the OAM mode cannot be switched at will after the traditional antenna array is fixed,a concentric array radial line slot antenna is designed.By optimizing the radial radius of the slot and the length of the slot,uniform radiation and phase excitation of the slot are realized.The radiation of l=±1,±2 in four modes was successfully generated by eight probes with constant amplitude and graded phase difference feeding at 14.25 GHz.The OAM bandwidth reached 26.7%,covering 13-17 GHz.Secondly,to solve the problem of low gain of circular RLSA,a spiral array radial line slot antenna is designed.Because the slots of spiral RLSA is closer and compact,the vortex electromagnetic wave with l=±1 and ±2 modes can be switched within 3032 GHz frequency band,which can obtain higher gain than circular RLSA and the maximum gain up to 24dBic.