Research On Ka-Band OAM Micro-Integrated Technology

Today,with the rapid increase of information transmission,spectrum resources are becoming increasingly scarce.Orbital angular momentum（OAM）has attracted much attention because it can carry a large amount of information.The different modes of orbital angular momentum are orthogonal to each other so that the electromagnetic waves carrying orbital angular momentum can theoretically transmit infinite modes at the same frequency point,thus effectively expanding the channel capacity.At present,the antennas that generate orbital angular momentum are mainly uniform circular array（UCA）antennas,while most of the traditional feed networks are complex and large,which need to be further integrated and miniaturized.The structures such as the patch antenna,the microstrip line and the substrate integrated waveguide are processed by PCB process,which is conducive to the system integration of the whole antenna array and feed network,thus achieving the purpose of greatly reducing the overall structure volume.At present,domestic electronic products with 5G technology mainly work in centimeter wave frequency band,while millimeter wave frequency band has not been fully utilized for data transmission.Therefore,it has a very broad prospect to study the orbital angular momentum technology in millimeter wave band,such as Ka band.This project adopts microwave multilayer printed circuit technology and three different micro-integrated structures to achieve the orbital angular momentum propagation with single mode,dual mode and reconfigurable multi-mode respectively:1.In order to achieve a high-integration between the power divider feed network and the patch antenna,so as to greatly reduce the device volume and achieve mass production.The radial power divider feed network made by substrate integrated waveguide like structure is used to realize the equal amplitude and phase output,so that the uniform circular array generates OAM mode l=1.The fixed cavity structure of coaxial line is designed for the coaxial through-wall connector.The overall simulation is carried out between the coaxial cavity fixed structure and the micro-integrated structure designed,and the influence of the coaxial cavity fixed structure on the antenna radiation is analyzed.The designed model is fabricated and the measured results verify the effectiveness of the design: the structure can generate OAM mode l=1 with high mode purity in Ka band.2.The micro-integrated structure of feed network whose output ports are equal amplitude with 45 phase difference and uniform circular array based on the T-junction is designed,and the scheme of using the patch antenna array to generate high-order OAM orbital angular momentum mode is proposed.In order to realize dual-mode transmission,the arrays that generate two orbital angular momentum modes（l=1 and l=-1）and their power divider feed networks are integrated on the same substrate,and the coupling between the arrays is reduced by adjusting the overall layout to ensure the highest mode purity of the two arrays.3.In order to realize the multi-mode switchable orbital angular momentum transmission micro-integrated structure,the PIN diode covering millimeter band is introduced to control the different phase delay lines which feed the patch antennas by controlling the breaking of the PIN diode,so as to adjust the phase difference of the entire array and realize the switch of orbital angular momentum of different modes.