Design And Research Of Vortex Wave Antenna Based On Resonant Ring

The increasing number of mobile terminal users has placed higher demands on the channel capacity of wireless communication,but research in the time,space and code domains has brought the efficiency of spectrum utilization close to its theoretical limit,and there is an urgent need to find a new wireless communication method to break through the development bottleneck.Vortex electromagnetic waves carrying Orbital Angular Momentum（OAM）have a promising application in expanding channel capacity due to their infinite number of modes and the orthogonality of different modes.The design of multi-mode vortex antenna with simple structure and low profile in RF band can promote the application of orbital angular momentum in wireless communication.This thesis will explore the design of vortex antennas by combining the basic theory of OAM and the working principle of traveling wave antenna.The main research contents are as follows.Firstly,the causes of the vortex electromagnetic wave generated by the conventional circular traveling wave antenna and the planar Archimedes spiral antenna is theoretically deduced and analyzed,in this thesis,the ring effective radiation region of planar Archimedes spiral antenna is abstracted,and two initial models of resonant ring traveling wave antenna with the resistance operating at 3 GHz are proposed.According to the phase of the radiated electric field,the two antenna structures can produce OAM modes of l=-1,-2 and l=+1,+2 respectively,and their reflection coefficients S₁₁ are below-10d B,with good return loss performance,but the electric field intensity distribution is not uniform and symmetrical enough.To address the shortcomings of the initial model,two improved models are proposed to enhance the symmetry of the structure and solve the problem of asymmetric electric field intensity distribution.However,because the above models are loaded with resistors at the end of the microstrip line to form the traveling wave current distribution,the gain of the antenna is low and further improvements are required.Secondly,on the basis of the improved model of resonant ring traveling wave antenna,a new structure of resonant ring traveling wave antenna without the resistance is proposed,which solves the problem of low antenna gain due to energy loss from resistance.The simulation results of HFSS show that the antenna can generate vortex electromagnetic waves with OAM modes l=0,l=±1,l=-2 at 3 GHz.Four feed points are used to feed the antenna.This structure can produce one more OAM mode l=-2 than the traditional patch array antenna.The performance of the vortex antenna was tested in the microwave anechoic chamber,and the feasibility of the antenna design is verified.The resonant ring traveling wave antenna designed in this thesis has a simple structure,low profile and can generate vortex electromagnetic waves with multiple OAM modes at the same frequency,which can promote the application of OAM multiplexing technology in the field of wireless communication and provide a reference for the development of vortex antennas.