| Summary: | 碩士 === 國立交通大學 === 電信工程研究所 === 103 === The thesis proposed an idea of designing a novel dual-band high impedance surface (HIS).The working frequency here are located at LTE-3.5GHz band and Wifi-5.2GHz band. In this thesis, CPW-monopole antenna and HIS are separated by air gap for impedance matching and validate the effect of HIS by overlapped simulation and experiment result. There are several ways to realize HIS and mushroom structure will be adopted here because of simplicity. By making a semi-symmetric structure on the upper metal sheet, it can obtain two different oscillating frequency. Further more, both frequency can be tuned independently because the LC parallel resonant cavities are separated.
The principle of HIS can explained by advanced electromagnetic theory. It says the reflection coefficient of conventional metal sheet is -1,so the reflected wave here must be destructive interference for incident wave which will cause low efficiency , low gain and mismatched if air gap is smaller than wavelength/4. On the other side , HIS as reflector can make the different effect because the reflection coefficient at working frequency is 1 ,which means the phase of reflected wave and incident wave are the same at the surface. For these reason, HIS will be used which arranged periodically as the reflector of antenna.
At last, the result shows that this kind of antenna can reduce the thickness of air gap by introducing the AMC reflector. Furthermore, the function of slot on the patch can increase the path of current to make the unit cell minimized and then the thesis will combine the idea for dual band design we have discussed. Finally, the thesis here can create small size and dual band HIS reflector.
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