Generation Of Vortex Electromagnetic Waves Based On SIW Antennas

Nowadays,the society is the information society.The increasing amount of information and the increasing speed of transmission have put forward higher demands on the wireless communication system,which leads to the rapid increase of wireless communication equipment,and may cause the phenomenon of channel blocking and frequency congestion.Orbital angular momentum(OAM)multiplexing technology is one of the most attractive solutions to solve this problem.Since different OAM modes are orthogonal,it can use this characteristic to modulate and demodulate signals,so the carrier electromagnetic waves have a new degree of freedom to improve the channel capacity and spectrum utilization in the wireless communication system.At present,the millimeter wave band has become the main frequency band of wireless communication,and the substrate integrated waveguide(SIW)is a promising design platform for the millimeter wave communication system,So the slot antenna based on the substrate integrated waveguide is widely used in the design of millimeter wave antenna because of its advantages of convenient design and compact size.The antennas that can generate and multiplex OAM beams is called vortex electromagnetic wave antennas.The core content of this paper is to design the vortex electromagnetic antennas based on SIW structure.Combining the orbital angular momentum multiplexing technology and the substrate integrated waveguide slot antennas is the biggest innovation in this paper.The theoretical knowledge of substrate integrated waveguide technology is introduced firstly,and its basic structure,transmission characteristics and the transition structures to other planar transmission lines are analyzed in detail,respectively.Secondly,according to the difference of the phase plane between vortex electromagnetic wave and conventional electromagnetic wave,we introduce the concept that what is the orbital angular momentum beams and how to produce the OAM beams.Based on above theories,the following three main findings are included in this thesis.1?An annular slot antenna based on circular SIW resonator is designed.The main structure of this antenna is a circular SIW resonator,and its main resonant mode is TM010 mode.By loading the metal perturbation holes and etching the different radius gaps on the SIW surface,the resonant mode of this circular SIW resonator can be changed: when the radius is 14 mm,it is TM110 mode,and when the radius is 11.5mm,it is TM210 mode.Then three probes are employed to feed into excitation with 120 degree phase difference,which results that two resonant modes rotate around the center.This antenna can form vortex electromagnetic waves through the annular gap.When working on the TM110 mode,the OAM beam mode is l=1,and the OAM beam mode is l=2 when working on the TM210 mode.2?An tunable phase shifter based on SIW is designed.Using phased array antennas to produce different modes OAM beams,the most important point is to design a feed network with different phase,so the importance of phase shifters is self-evident.This phase shifter embedes metal inductive holes on the fundamental SIW and etches a series of slots on the SIW surface.8 PIN diodes are loaded on each slots.By adjusting the positive and negative of bias voltage,the PIN diodes can be in the conduction or cut-off state,thereby regulating the "open" or "off" state of the slot.Each group of slots is equivalent to the step of phase adjustment,and the sensibility holes can increase the step length.Through selecting the number of opening or closing steps,the phase range of 0~180 degree can be adjusted.3?A eight sided phased array antenna based on triangular SIW resonators is designed.This array antenna employes 8 triangular SIW resonant cavity antennas as radiation units.The radiation slots of each array elements is tangent to a circumference with certain radius.The array antenna can radiate OAM beams fed by the excitation with same amplitude but different phase on each radiation units.When the feed phase difference between two adjacent units is ?? = 0°,45°,90°,135°,this antenna can generate OAM beams with mode number l= 0,1,2 and 3,respectively.