Design Of Low Profile Antennas Based On Periodic Structures

With the rapid development of artificial electromagnetic structure,periodic structures has been applied in microwave antennas,which always behaves as a method of realizing artificial electromagnetic materials.In this thesis,several low profile antennas are proposed based on the electromagnetic properties of artificial magnetic conductor(AMC)and partially reflective surface(PRS).1.The equivalent circuit model of AMC structure is studied,while its properties of zero reflection,high impedance and surface wave bandgap are analyzed in theory.A Infinite periodic unit of rectangular ring is simulated by ansoft HFSS,and the influence of its main parameters on its electromagnetic properties is analyzed.2.A low profile antenna based on resonant cavity is designed.By using the ray tracing model,the resonant conditions is analyzed,and several cases of ultra-low profile are proposed.Based on double-sided printing structure,a PRS element is proposed and its electromagnetic properties are simulated.Combined the PRS with micro-strip patch antenna,the low-profile antenna based on resonant cavity is obtained.With the use of short column,the cross-polarization is improved obviously.The experimental results show that with the aperture size of 1.56?×1.56? and cavity height of ?/8,the impedance bandwidth is 8.44-8.76 GHz with VSWR less than 2,while its maximum gain is up to 13.3d Bi.3.An AMC structure with air gap is designed and its structural parameters are optimized.By using the AMC structure as the reflector of the traditional dual-polarized antenna,a low profile dual-polarized base station antenna is proposed.The profile of the antenna has been reduced from ?/4 reduced to ?/8.Finally,the simulation and experiment were carried out and the results are quite consistent.The experimental results show that both two ports of the proposed design obtained a wide bandwidth(2.08–2.80 GHz)with VSWR less than 2,while its maximum gain is up to 9.17 d Bi.