Application Of High Impedance Surface In The Plane Of The Antennas

This thesis is focused on the application of high-impedance surface in the design of antennas and antenna arrays. High-impedance surface is one kind of electromagnetic band-gap structures, which consist of metal and dielectric substrate. The period of the high-impedance surface is much smaller than one wavelength. It has the property of suppression of surface waves, and in-phase reflection in certain frequency bands as well. Due to these two properties, the high-impedance surfaces have been widely used in microwave circuits and antennas. The novel high-impedance surfaces with special performances like multi-band, wideband and small size, has also attracted much attentions from the researchers.The main works are concerned on the application of high-impedance surface in antennas and antenna arrays, and are outlined as follows. Firstly, the properties of suppression of surface waves and in-phase reflection of the high-impedance surface are analyzed. And the influences of the parameters on the two properties of mushroom high-impedance surface and the in-phase reflection property of obliquely incident waves are investigated. Secondly, aiming at the applications of the high-impedance surface in the antenna array with small element distance, a compact single fork-like high-impedance surface is designed, which can reduce the mutual coupling among antenna elements. When employed in beam scanning array, the impedance matching can be significantly improved especially in the case of large scanning angle, thus causing larger scanning range. Then, a dual-band antenna based on planar inverted cone antenna is proposed. The frequency ratio and impedance matching can be adjusted flexibly without changing the size of the antenna. A dual-band high-impedance surface is also designed to achieve a low-profile dual-band antenna combined with the dual-band monopole antenna. Lastly, the concept of variable polarization high-impedance surface is proposed with metal strips with45degree and high-impedance surface. When employing it in the linearly polarization monopole antenna, circularly polarization can be achieved in certain frequency band. Finally, two directional variable polarization high-impedance surface is designed, and a dual-band circularly polarization antenna is realized accordingly.