Research On A Beam Switchable Microstrip Antenna Based On Characteristic Mode Analysis

With the advent of the 5G era,beam-switchable and scannable antennas have received extensive attention and have important theoretical and application value.Combining the characteristic mode analysis?CMA?and multi-mode coupling,several high-performance antennas with beam switching and scanning are designed in this paper.The specific research content can be divided into the following three points:?1?Based on CMA,a vertically polarized patch antenna with switchable endfire beam is proposed.Introducing shorting pins into the array composed of three rectangular patches moves Mode J₃with beam direction perpendicular to the array to other frequency,while Mode J₁and Mode J₂with bidirectional beam along the array direction have a phase difference of 90°at the resonance point.Using the mode couple concept,finally a near-endfire radiation pattern is generated with a gain of 5.19d Bi,the beam tilt angle at 2.17GHz can reach 60°,where the side lobe level down to-15d B.The beam can be switched when the feed is converted between two sysmmetrical ports.?2?Based on CMA,a beam switchable microstrip Yagi antenna with beam scanning,high gain,and low side lobe level characteristics is proposed.There are four modes in the 4-element array:Mode 4,Mode 5,Mode 7 and Mode 9.As the frequency increases,the mode changes from broadside to bidirectional beam parallel to the array direction,and the tilt angle increases sequentially.Introduce and adjust the shorting pins to realize the couple of the adjacent modes.In this way,the side lobe of Mode 7 and Mode 9 are suppressed and finally frequency beam scanning is realized at3.2GHz-3.335GHz,the beam can be scanned uniformly from 14°to 51°.The measured gain of the antenna is as high as 9-10d Bi,and the side lobe level from 3.215GHz to3.295GHz is below-20d B.Feeding different ports can realize beam switching.?3?The beam switchable microstrip antenna has been further researched.Firstly,the unit of array is added and we propose a five-unit Yagi array.A beam scanning of 18°to 53°can be achieved when the modes are coupled effectively,and the radiation gain of the maximum beam tilt angle is 10.9d Bi.The array also has low side lobe level and beam switchability.Finally,a cross-shaped four-beam switchable antenna is designed.Through the design of the dielectric substrate and the ground,the surface current is controlled and the mutual coupling between two orthogonal modes is reduced,and the beam can be switched in horizontal direction between 0°,90°,180°and 270°when we feed separately in different position,the maximum tilt angle of the beam reaches 70°,where the gain is 5.23d Bi.This paper uses the principle of mode coupling to design the antenna and improve the radiation performance of multi-element microstrip antenna,at the same time the antenna has switchable beam,which is more advantageous than traditional endfire antennas.