Research On Tightly Coupled Antennas For 5G Mobile Communication

With the announcement of the 5G cellular communication frequency band,the base station antenna with traditional structure designed for 5G application hardly has sufficient bandwidth to cover 2,3,4G operation bands.Herein,it is of practical significance to develop a broadband base station antenna that can cover 2,3,4,and 5G mobile communication bands simultaneously.Recently,the tightly coupled array antennas has been extensively investigated,being different from traditional array antennas in avoiding the mutual coupling between array elements,it achieved bandwidth expanding of the tightly coupled array antenna and system miniaturization by effectively utilizing the mutual coupling effect between the array elements.Based on the theory of base station antennas and tightly coupled array antennas,the tightly coupled antenna is studied by combining with the resistive frequency selective surface.The main contributions are as follows:1.Based on the principle of tightly coupled array antennas,a broadband 5G base station antenna with tightly coupled structure is proposed.The antenna is composed of a pair of orthogonal bowtie-shaped dipoles.The impedance bandwidth of the antenna is effectively broadened by the coupling effect between the adjacent dipoles.In addition,by loading a resistive frequency selective surface between the antenna and the metal reflector,the resonant reflected wave of the reflector is absorbed,and the radiation performance of the high frequency band is improved.Finally,the antenna achieves good performances such as: a dual polarization VSWR smaller than 1.5,an isolation between two ports higher than 55 dB,a cross polarization discrimination larger than 10 in the range of +/-60°,a half power beam width of 65° +/-5° and an in band gain greater than 8.5 dBi within 1.7-3.6 GHz frequency band.The structure is finally fabricated and tested.The measurement results agree weel with the simulation results,which indicate that the tightly coupled array antenna is effective and feasible in the design of the base station antenna.2.A tightly coupled array antenna for 5G mobile communication is proposed.For eliminating the short-circuiting effect caused by metal reflector,a resistive frequency selective surface is loaded,and a matched feed structure is designed.For infinite array,a dual polarization VSWR smaller than 1.5 and an isolation between two ports higher than 30 dB are achieved within 1.3-5 GHz frequency band.Finally,the truncation effect and the compensation of the truncation effect of the tightly coupled array antenna are studied by simulating the semi-infinite tightly coupled array.