Wide-angle Scanning Gradient-Index Lens Antenna

Millimeter-wave(MMW)communication systems are widely used due to their vast spectrum to provide high data throughput,such as point-to-point and point-to-multipoint communication systems,WIFI systems,radars,etc.However,due to high path loss in MMW band,high gain and electronic beam-steering antennas are urgently desired in MMW communication systems.Recently,lens antennas have considerably attracted attentions of researchers and competitive due to their large-angle scanning ability.This thesis focuses on the high-direction and wide-angle scanning lens antenna,and effective solutions and methods are proposed.Two gradient-index lens antennas are designed based on the proposed method.The main work contents are as follows:An effective design method for complex and large-size GRIN lens antennas is firstly proposed,which contains an initially rough design of lenses and two staged optimizations.Based on the geometry optics,the shape of lens antenna is designed.In the optimization,the adopted quasi-2D models of lens antennas provide the similar simulation results with those of 3-D lens models whereas the computational times of the quasi-2D models are greatly reduced and acceptable for optimizations.Besides,in this method,the determination of excitation coefficients of the elements requires only once 3-D full-wave simulation of the whole antenna.Therefore,the design approach is effective and suitable for large-scale GRIN lenses.Following the proposed design procedure,this paper explores the design of two gradient-index(GRIN)lenses lens antennas respectively operating at 28 GHz and 39 GHz for 5G wireless communication.The proposed antennas consist of novel GRIN antennas and phased array antenna(PAA)feeds which contain several aperture-coupled microstrip antenna(ACMA)elements.The lens antenna at 28 GHz exhibits a wide and continuous scanning coverage from 0° to 58° with high gain,while the lens antenna at 39 GHz shows an extreme scanning coverage from 45? to 80? with acceptable gain.To verify the design method,the lens operating at 28 GHz is fabricated and measured.The measured results show that the scanning angle can cover about 58° with 3.1-dB gain drop thus confirming the simulation results.