Microstrip Antennas Designed By Electromagnetic Metamaterials

Metamaterial is a kind of artificial composite structure or material that can provide unique electromagnetic characteristics which do not usually exist in nature.This dissertation uses the unique electromagnetic properties of the metamaterials to design microstrip antennas.By theoretical analysis and full-wave simulation,the designed metamaterial units can meet the requirements and improve the performance of the traditional antennas.The dissertation is divided into two sections.Section 1presents two types of Fabry-Perot cavity antenna which are based on metamaterials periodic structures.Section 2 presents two types of dual-band microstrip antenna which are based on CRLH-TL units.The main contributions of the thesis are listed as following:1.Two types of Fabry-Perot cavity antenna based on the metamaterial periodic structures are proposed.The first one is broadband high gain F-P cavity antenna with frequency selective surface(FSS)cladding.The double-layer FSS unit has wide band characteristics which can improves the gain bandwidth of the antenna effectively.The1 d B gain bandwidth of the antenna is 10.7%.It has been significantly improved compared to the traditional F-P cavity antenna(1d B gain bandwidth is about 5%).The gain of the antenna is 14.1d Bi at the center frequency 9GHz.The second one is low-profile F-P cavity antenna with electromagnetic band gap(EBG)structures.The height of the cavity is reduced by half by using the in-phase reflection characteristic of the uniplanar EBG structures.The gain of the antenna is 14.5d Bi at the center frequency 9GHz.2.Two type of dual-band microstrip antenna based on the CRLH-TL units are proposed.The first one is dual-band microstrip monopole antenna which is designed by using the phase lead feature in the left-handed band of the CRLH unit.In this design,we propose a novel CRLH unit.The unit has symmetrical structure.When introducing the unit into the monopole antenna,the phase compensation provided by the unit can generate a low resonant frequency so that the antenna can obtain the second work band.The antenna gets the gain of 2.29 d Bi and 1.13 d Bi at 1.54 GHz and2.4GHz respectively.The second one is dual-band compact microstrip patch antenna based on CRLH periodic structures.We proposed an improved CRLH unit which has low left-handed band.The CRLH periodic structures can generate a left-handed resonant frequency.By inserting a 2×2 CRLH unit array into the middle of the patch,the antenna works at dual band and narrowed 85.3% than the traditional patch antenna.The overall size of the antenna is 0.19?₀×0.19?₀×0.03?₀.The antenna is fabricated and measured.The measured results are in good agreement with the simulated results.