Study On High-Gain Metamaterial Superstrate Antennas And Its Beam-Control

Metamaterials have been an attractive topic because of their unique feartures with unusual physical phenomena or superior performance. It's a new subject that applies the metamaterials to antenna field by controlling electromagnetic waves to improve the feature of antennas. Metamaterial superstrate antenna is a combination of antenna and metamaterials which is studied and used in a wide range of application. The high-gain property and beam control ability of metamaterial superstrate antennas that frequency selective surfaces(FSS) act as superstrates is mainly investigated in this thesis. Based on the bandpass and bandstop FSS, we study the high-gain resonant cavity antenna and beam controlling transmitarray antenna respectively.Firstly, A low-profile high-gain resonant cavity antenna is designed to realize slight beam steering and a high-gain transmitarray antenna is designed to realize large-angle beam steering. Then a circular polarized transmitarray antenna is designed with high-gain and beam steering. This thesis clearly reveal the realization of high-gain and beam controllingby use of metamaterial superstrate antennas.The main contributions of this dissertation are summarized as follows:1.A low-profile resonant cavity antenna composed of ameliorated fishnet elements is presented. And the superstrate FSS of this antenna is modulated based on the half-gradient phase theory to form two half-uniform FSSs which act as the superstrate of beam steering antennas. The first antenna achieves a 10°tilted beam, and the second one achieves a 19° tilted beam.2.Multi-layer Miniaturized FSS(MMFSS) element is used which consists of metal patches and rings based on the synthesis technology of multi-layers FSS. By varying the parameters of the MMFSS element, a phase-shift ranging of 310° is achieved for transmitarray to fit phase compensation of designing transmitarray. Then the transmitarray antennas are designed by use of the transmitarrays which consist of different size MMFSS elements and a horn antenna acting as the excitation. The main beam of these transmitarray antennas is steered to different direction, scanning from 0° to 57° in elevation plane and arbitrary angle in azimuth plane.3.The perturbation is introduced into MMFSS element to form Circular-polarized Miniaturized FSS(CMFSS) element with the property of converting linearly polarized wave to circular polarized wave. Likewise, we utilize the variation of the size of CMFSS element to achieve a phase-shift of 360° to fit the phase compensation. Circular polarized high-gain transmitarray antennas with broadside beam are designed with CMFSS elements and horn antenna acting as excitation. The range of the beam scaning is from 0° to 45°.