Research On High Impedance Surface EBG Structures Applying To Antennas

The purpose of this thesis is to investigate how to use High Impedance Surface (HIS) to reduce the height of a broadband and high-gain printed antenna constructed from a Fabry-Perot resonator.The HIS is made up of metal and dielectric materials. It has not only the property of suppressing surface wave as well as one kind of Electromagnetic Band Gap (EBG) structure, but also the feature of positive reflection coefficient (+1) rather than negative (-1) from an electric-conductor surface within a limited frequency range. In this case, the HIS can be considered as an Artificial Magnetic-Conductor (AMC) to replace the ground plane of antenna for decreasing the profile. In the case for antenna application, the reflection phase of oblique incidence at HIS must be considered. In this thesis, several types of HIS with periodic square lattices are analyzed for comparing their sensitivities of reflection phase to the incident angle. The results show that the mushroom type and square patch type HIS have least sensitivity to the incident angle.Based on the previous study, a Fabry-Perot resonator antenna structure with double-layer superstrates (lower dielectric layer and upper dielectric EBG layer) and a microstrip-line fed aperture radiator on ground plate had been proposed. Its superstrates provide high gain, its aperture radiator possesses broad bandwidth for impedance; however, the bandwidth for gain (?3dB drop) is narrower, side-lobe is high, and the structure has at least half-wavelength profile. In this thesis, two types of improved Fabry-Perot resonator antennas are developed, in which a rectangular patch with U-shaped slot is adopted as broadband radiator and surrounded by HIS. By means of optimizing most of structure parameters respectively, they keep high gain by employing the superstrates; extend the common bandwidth of both impedance matching and gain stable; reduce obviously the height of profile; and also decrease the side-lobe level.The simulation work is done with CST Microwave Studio. Two improved Fabry-Perot resonator antennas are also fabricated and measured. The measured data has proved the accuracy of simulated results.