Research On Circularly Polarized Antenna Loaded With Multi-layer Frequency Selective Surface

In recent years,with the development of Frequency Selective Surface(FSS),the application of FSS in all aspects has made great progress.This thesis focuses on the research of FSS loaded circularly polarized antenna,including the circularly polarized antenna based on FSS linear-to-circular polarization converter and the circularly polarized Fabry Perot resonator antenna based on FSS.First of all,a multilayer non-resonant FSS structure consisting of two layers of patches with square corner,one layer of cross grid lines with slot and two layers of thin dielectric layers is proposed.Based on this structure,a linear-to-circular polarization converter is developed,which has the characteristics of small size,low profile,wide band and high in band transmittance.Based on this linear-to-circular polarization converter,two kinds of circularly polarized antennas are designed.One is the circularly polarized horn antenna,which uses the standard horn antenna working at X-band as the feed.According to the aperture size of the horn antenna and the reasonable design unit number.The actual measured internal impedance at 9 GHz – 12 GHz is less than-10 d B,the axial ratio bandwidth is 19.7%,and the maximum gain is 20.6% d B,the radiation efficiency is 80%;the other is the 2 × 2 linearly polarized patch array,which can also achieve good performance polarization conversion.Secondly,a partially reflection surface based on FSS is designed,which has more than 0.56 reflection coefficient amplitude and positive slope reflection coefficient phase.In order to expand the feed bandwidth,a single feed point circularly polarized patch antenna with truncated corner and slot is used as the feed to design a circularly polarized F-P resonator antenna.The simulated 3-d B axial ratio bandwidth is 4.3%,and the impedance bandwidth is22.2%.In order to further expand the bandwidth,a 2 × 2 circularly polarized patch array with truncated corner and slot is obtained by using the sequential rotary feeding method.As a feed,the circularly polarized F-P resonator antenna is designed.The actual measured impedance bandwidth is 26.9%,3-d B axial ratio bandwidth is 17%,peak gain is 15.4 d B,and the radiation efficiency is 86.8%.