Study On Bid Irectional Radiating Antenna Based On Metasurface

The bidirectional radiated antenna can control the beams in the two half-area at the same time,which can effectively improve the channel capacity,diversity gain and coverage of signal propagation,showing great advantages in multiple wireless communication systems.However,the traditional bidirectional antenna has the problems of difficult design,high insertion loss and low radiation efficiency due to its feeding network,leading to difficultly achieving high gain.In recent years,metasurfaces have been widely used in the design of bidirectional radiating antennas because they can achieve efficient regulation of the amplitude,phase,and polarization of electromagnetic waves without increasing the fabrication cost and feed complexity.However,the existing bidirectional radiating antennas based on metasurfaces have shortcomings such as narrow bandwidth,single function,and inability to flexibly control the radiation beam.Aiming at the above problems,this paper proposes a novel antenna scheme,and designs two broadband bidirectional radiated antennas using this antenna scheme.(1)The novel antenna scheme consists of upper transmitarray(TA),lower TA and feed antenna mounted between the two TAs.Using this scheme,the bidirectional antenna can switch the function mode of TA and FTA by the energy distribution of the transmitted and reflected waves in the upper and lower half spaces on the basis of controlling the polarization of feed antenna,leading to the ability of the unidirectional or simultaneous bidirectional radiation regulation.(2)A broadband high-gain bidirectional radiating antenna is designed.The upper TA and the lower TA are both composed of polarized rotating metasurfaces,and the feed antenna is a Vivaldi antenna.The proposed bidirectional radiating antenna can achieve forward and backward radiation with maximum gain of 21.1 d Bi and 22.5 d Bi,respectively,and maximum aperture efficiency of 40.9% and 24.9% in the frequency range of 8 GHz-12 GHz.In the bidirectional radiation mode,the forward and backward maximum gains are 18.3 d Bi and 19.1 d Bi,respectively.On this basis,the bidirectional antenna is improved by replacing the lower TA with a co-polarized metasurface,so that the polarizations of forward and backward radiation beams are identical.Therefore,the forward and backward radiation beams polarizations of the proposed high-gain bidirectional radiating antenna can be orthogonal or the same,which has high practicability in modern communication systems.(3)A broadband bidirectional radiating orbital angular momentum(OAM)antenna is proposed.The antenna also adopts the proposed bidirectional antenna scheme and uses the method of combining the converging metasurface phase and the vortex metasurface phase to generate forward,bidirectional and backward OAM beams.The simulation and actual measurement results show that the designed bidirectional OAM antenna has the following advantages: 1)It can achieve broadband vortex beams from 8 GHz to12 GHz.2)It can control the three working states of forward,backward and simultaneous bidirectional radiation 3)Three kinds of the mode purity in the working state is higher than 90%.