Circularly Polarized Metasurface Antenna

Nowadays,the researches of antennas with high performance and multifunction become more and more popular as the rapid development of wireless communication systems.However,the traditional antenna's theory and application has been very mature,it is difficult to further improve the antenna performance by using traditional antenna.The emergence of metamaterials brings new breakthroughs to this problem.Recently,two-dimensional metamaterials,which widely known as metasurface(MS)structures,have been widely used in the design of antennas.On the other hand,to reduce the polarization mismatch and multipath fading,circularly polarized(CP)antennas are greatly demanded.The MS can be used to generate CP waves.When it is applied to the design of CP antennas,compact structures and stable CP characteristics can be realized.This paper presents a series of researches on CP MS antennas to obtain high performance,such as high gain,filtering response and wide axial ratio(AR)bandwidth.The main work can be summarized as follows:1.High gain differential-fed circularly polarized metasurface antenna:A CP MS antenna fed by a pair of differential feeding structure operated at 6.4 GHz is proposed here.Compared with traditional single-ended CP MS antenna,the simulating results show that:the proposed differential-fed one can obtain a wider bandwidth and a high gain,which can reach 10.1 dBic in the operation band.2.Differential-fed circularly polarized filtering metasurface antenna:To construct a filtering antenna,the proposed differential-fed CP MS antenna is integrated with a filtering balun.The differential-fed CP MS filtering antenna is designed at 6.1 GHz,and a peak gain of 9.45 dBic can be obtained.Finally,a differential-fed CP MS filtering antenna with an improved filtering balun structure is proposed,which can achieve wider impedance-AR bandwidth,higher gain and better out-of-band suppression level.3.Broadband circularly polarized metasurface antenna array:A 2×2 sequential rotating-fed CP MS antenna array based on the single-ended CP element is presented to achieve an improved AR bandwidth and gain performance.Firstly,a sequential rotating feeding structure is designed with the performance of an in-band amplitude imbalance of about 0.5 dB,a phase difference of ±4°,and insertion loss of 0.65 dB.Then a 2×2 broadband CP MS antenna array at6.3 GHz is obtained with a peak gain of 14.24 dBic.