Research On Fan Beam Planar Lens Antenna

With the development of metamaterial,planar lens antennas composed of phase shift surfaces(PSS)have received more and more attention.Planar lens antennas have many advantages such as high gain and small size.By adjusting the arrangement of phase shift unit cells,the shape of electromagnetic wave radiated by lens antennas can be controlled.The arrangements of the phase shift unit cells that can emerge the pencil beam,fan beam and vortex beam are mainly studied in this thesis.According to the computed results,a high gain pencil beam plane lens,fan beam lens with different beam widths and vortex beam lens with different orbital angular momentum(OAM)modes are designed.The above-mentioned antennas are proved having good performance after simulation.The chief contributions in this paper are as follows:Firstly,a new structure of phase shift unit cells working in the 76.5GHz is introduced.The structure has three conductor layers and two dielectric layers.The thickness of this kind of unit cells is about 0.125? which is much smaller than that of the dielectric lens working in the same band.The phase shift unit cells can achieve a phase shift with range of 0?360°,and have a high transmission coefficient.In order to reduce the difficulty of manufacture,the entire phase shift range is divided into 8 subranges,and only the median value of phase shift in every 8 subranges is used.The designed lens antennas still have good performance.On this basis,the distribution of the phase shift unit cells on the surface of the pencil beam plane lens antenna is studied,and different phase shift values are given according to the difference of electromagnetic wave path to convert the spherical wave radiated by the feeder into a plane wave,so the gain of the antenna is greatly improved.The gain of the pencil beam planar lens antenna designed is as high as 32.1d B,which is 20 d B higher than that of the feed antenna.By adjusting the phase shift gradient change rate of the lens,fan beam antennas with different beam widths are designed.The gain of the lens antenna reaches 30 d B.The beam widths on the E and H planes are 1.7° and 4.1°,respectively.When the gradient change rate increases to 2,the gain of the lens antenna reaches 24.2d B,and the beam widths on the two main planes are 1° and 18.3°,respectively.In addition,this article introduces the propagation of vortex beams carrying orbital angular momentum,and studies the design of single-mode vortex beam plane lens antennas.By giving different phase shift values to incident electromagnetic waves at different azimuth angles,the phase of the electromagnetic wave can be made spiral,and the sign of the mode number corresponds to the direction of rotation of the phase shift value,and the absolute value 7)of the mode number indicates the phase shift value changes by 2pl when the azimuth angle rotates one circle.Finally,the singlemode vortex beam plane lens antenna with mode numbers of +1,±2,+4 was designed,and then a multi-mode vortex beam plane lens antenna with mode numbers of +1 and +2 was designed by combining inner and outer layer.The factors affecting the performance of the lens antennas were analyzed,and the above-mentioned antennas have achieved good performance.