Circular Polarized Antenna With Metasurface

This paper introduces the development of the antenna and the development of metamaterials at home and abroad,and introduces the basic parameters of the antenna and the basic types of metamaterials.In this paper,the different technical routes of circular polarization of microstrip antennas are introduced and analyzed.The circular polarization theory and cavity mode theory of single-feedback circularly polarized antenna are deduced to understand the influence of geometric perturbation on the generation of degenerate modes.Then,the principle of circular polarization is studied,and the 5.8GHz slot antenna and meta-surface are designed.The meta-surface consists of 4*4 periodic units,is in the square metal surface irregular slotted design,its role is equivalent to a circular polarization function of the spatial filter.After loading the meta-surface,the linearly polarized wave of the slot antenna can be transformed into a circularly polarized wave,the impedance bandwidth of the slot antenna is 5.70-5.96GHz,and the axial ratio bandwidth of the circular polarized wave is 5.03-6.22GHz,gain is 6dB,the meta-surface can also shield the electromagnetic interference outside the working band.However,since the meta-surface area is too large and is not suitable for a reader antenna having a high degree of miniaturization,the miniaturization method of the meta-surface is studied.The structure of the slot antenna is the same,the meta-surface is only 1/16 of the size of the previous meta-surface,but the meta-surface loading method has changed and needs to be tightly fitted to the back of the microstrip slot patch antenna.After loading the impedance bandwidth is 5.65-6.05GHz,the original axis ratio of the slot antenna is 60dB,after loading the meta-surface AR is reduced to 10dB,with two-layer meta-surface AR is reduced to 5dB,with three meta-surface axle ratio is reduced to less than 3dB,the AR bandwidth is 5.52-5.64GHz.It can be seen that the increase in multi-layer meta-surface,the antenna AR bandwidth can be extended,the AR will be reduced.In addition,since the thickness of FR4 is increased and the equivalent permittivity is increased,the center frequency is lowered.Finally,the effect of the meta-surface rotation angle on the polarization state is studied.The structure of the slot antenna is unchanged and the size is adjusted.The impedance bandwidth is 5.53-5.90GHz.When the meta-surface and slot antenna alignment,you can achieve left-handed circular polarization,the AR bandwidth is 5.74-5.85GHz,when the meta-surface rotate 90 degrees,you can achieve right-handed circular polarization,the AR bandwidth is 5.78-5.94GHz.The volume of the circularly polarized antenna is only 25mm*25mm*4mm.Polarization state principle is different angles of the meta-surface will produce different impedance phase difference,the phase difference will produce different states of the circular polarization wave,circular polarization in the opposite direction of rotation.