Design Of High-gain And Ultra-wideband End-fire Antenna Based On Metasurface

With the rapid development of wireless communication technology,and the increase of various working frequency bands,new requirements have been put forward for communication systems.As a key component of wireless communication systems,antenna is facing more and more challenges.In particular,in order to guarantee the quality of the received signal and the coverage range of the system,the antenna needs to possess high gain and wideband characteristics.Therefore,how to improve the gain of ultra-wideband(UWB)antenna has become one of the hot topics in current research.In this paper,the gain enhancement of UWB end-fire antenna is studied and designed based on the metasurface,including the design of Vivaldi antenna and Quasi-Yagi antenna.The main research contents are outlined below:(1)A UWB double slot Vivaldi antenna(DSVA)loaded with the semi-elliptical slots and a novel wideband non-resonant metasurface is designed.The semi-elliptical slots are etched on both sides of the ground plan of the DSVA to improve the current distribution,thereby improving the radiation of the antenna.In addition,the nonresonant high refractive index unit cell is designed,and the non-resonant characteristics of the structure is verified by S-parameters.The equivalent electromagnetic parameters of the unit cell are extracted by using the equivalent parameter extraction method.,and can maintain a stable high refractive index in the operating bandwidth of 1-18 GHz.The unit cells are arranged in a periodic pattern on the DSVA to form the metasurface,which can bend the outgoing wave to the end-fire direction and improve the gain of the antenna.The return loss of the antenna is less than-10 dB in the frequency range of 2-13.4 GHz,while the gain of the proposed antenna is 6.4-16.3 dBi with a maximum gain enhancement of 3.1 dB.(2)An ultra-wideband high-gain quasi-Yagi antenna based on improved structure and linearly polarized reflective metasurface is designed.Firstly,the structure of the quasi-Yagi antenna is improved by adding stubs on the ground plane and changing the driver dipole to the butterfly shape,which can broaden the operation bandwidth of the quasi-Yagi antenna.The impedance bandwidth is expanded by 18% compared with the original antenna.Butterfly-shape directors are added to the top and bottom surfaces of the dielectric substrate,which improves the gain of the quasi-Yagi antenna with a maximum gain enhancement of 1 dB.Then,a linearly polarized reflective unit cell is proposed.By calculating the phase of the metasurface,a reflective focusing metasurface is designed.The focusing effect of the metasurface is verified by simulation.The radiation performance of the quasi-Yagi antenna is improved by applying the focusing effect of the metasurface.The return loss of the antenna is less than-10 dB in the frequency range of 5.6-18 GHz,while the gain of the proposed antenna is 7.6-18.5 dBi with a maximum gain enhancement of 12 dB.