| After entering the 5G era,the electromagnetic environment becomes complex,which puts forward higher requirements for wireless communication system.As an important RF passive device,antenna needs to have the characteristics of multi-function reconfiguration,broadband tunability and RF front-end integration.In recent years,the reconfigurable antenna has been realized through a variety of liquids,which brings more designable elbow room and has great potential for development.Firstly,this paper introduces the relevant research background and significance,and summarizes the reconfigurable antenna.This paper classifies the reconfigurable methods and focuses on the liquid adjustment mode of reconfigurable antenna.Then the working principle of antenna and related theoretical knowledge involved in this paper are briefly described,and the engineering experience formula is given in combination with the specific form.Finally,based on the above contents,four reconfigurable antennas are designed,which have different characteristics.They are briefly described as follows(1)Low-Profile Broadband Polarization Reconfigurable Liquid Metal Antenna.The antenna is coplanar waveguide structure and adopts active liquid reconfigurable type.By changing the position of liquid metal,the switching of LP,LHCP and RHCP operating modes is realized.Finally,the designed antenna works in the RF frequency band of 2.45 GHz,the relative impedance bandwidth of circular polarization is greater than 34.6%,the in-band gain of the three polarization modes is greater than 5 d Bi,and the cross-polarization suppression is greater than 17 d B.(2)Polarization Reconfigurable Filter Liquid Metal Antenna.Based on the design(1),the multi-branch feed structure is adopted,so that the antenna has three transmission zeros to realize the filtering characteristics.The antenna realizes the same polarization reconfigurable function as design(1)by changing the position of liquid metal in PDMS structure.Finally,the designed antenna filter zero point and polarization mode can be adjusted independently.The operating frequency is 5G TDD N77 communication band,the peak gain is 4.7 d Bi,and the out of band suppression of the three polarization modes is greater than-13 d B.(3)Polarization-and Frequency-Reconfigurable Patch Antenna Using Gravity-Controlled Liquid Metal.Based on the previous two designs,a passive reconfigurable antenna controlled by gravity is designed to highlight the fluidity of liquid metal.The application scenario of the antenna is vehicle communication,which can deal with complex terrain environment and slope attitude,and basically covers the common vehicle networking frequency band.Finally,the antenna has four reconfigurable frequency bands(1.2-1.6 GHz,2.5-2.75 GHz,4.2-4.55 GHz,and 5-5.4 GHz)and three polarization modes(LP,LHCP and RHCP)in different states.The gain in different modes is greater than 2.6 d Bi,and the pattern stability in the operating frequency band is good.(4)Broadband Polarization Reconfigurable Liquid Dielectric Resonator Antenna Controlled by Gravity.To study the liquid antenna and optimize the gravity controlled liquid antenna in design(3),we combine ethyl acetate with passive reconfigurable mode to realize a liquid dielectric resonator antenna with variable polarization mode more comprehensively.The antenna can switch between LP(2-3.17 GHz),LHCP(2.16-2.84 GHz)and RHCP(2.25-3.2GHz),and the corresponding peak gain is 7 d Bi,6.9 d Bi and 7.2 d Bi respectively.The antenna has the broadband,and the coverage ratio of circular polarization bandwidth and impedance bandwidth is high. |
