| Microwave photonic crystal is also called electromagnetic band gap (EBG) structure, which can be divided into conventional mushroom electromagnetic band gap (CMT-EBG) and uniplanar compact electromagnetic band gap (UC-EBG). The structure possesses two unique properties:in-phase reflection band gap and forbidden band gap. Surface wave impedance changes along with the frequency. To meet the need of Radio Over Fiber communication system on millimeter wave antenna, the advantages of wideband and high gain can be obtained by use of the EBG structrues’special properties. The main results of the thesis are as follows:Firstly, this paper presents a study on CMT-EBG to further improve the ultra wideband monopole antenna performance. The original antenna has a bandwidth of9.27GHz (1.73-11GHz) that covers PCS, UMTS, Bluetooth, LTE, WiMax, and UWB frequency range. While the bandwidth of the antenna with CMT-EBG embedded on both sides of50Ω microstrip line can be enhanced to9.47GHz (1.53-11GHz) with the extra GPS, DVB-H, and DCS covered. The largest impedance bandwidth of151%can be obtained. Moreover, the comparisons of gain characters as well as the radiation patterns are discussed at the bands of interest. It is illustrated that the gain of the antenna based on CMT-EBG is higher than other two cases except to the range of5.19to5.93GHz and the radiation patterns are basically identical. The antennas are fabricated on FR4substrate and the deviations between measured results and simulated results are discussed.Secondly, this paper presents a study on the60GHz magneto-electric (ME)-dipole antenna. The design of4x4ME-dipole antennas planar array on low temperature cofired ceramic (LTCC) substrate are proposed. The result shows that the peak gain is up to17.67dBi at60GHz. It is revealed that our design satisfies the60-GHz standards ruled by IEEE802.15.3c. However, the structure and size of antenna array is complex. In order to solve the ploblem, the CS-UC-EBG is etched around the radiator patch of ME-dipole antenna. Gain enhancement is achieved without deteriorating the previous impedance bandwidth of more than33%from50to70GHz. The maximum gain is increased from7.7to11.7dBi. Many advantages, such as low cost, easy fabrication, wide bandwidth and high gain are presented.Finally, this paper presents a study on bidirectional symmetrical I-shaped slot uniplanar compact electromagnetic band-gap (BSIS-UC-EBG) structure to further improve the optically transparent monopole antenna performance. The original antenna is fabricated in a conductive and transparent material which is made of a gold layer deposited on a0.2-mm-thick fused silica7980Corning substrate{εr:3.8and tanδ:0.0001). The antenna has an impedance bandwidth of20.2%(55.5-68GHz) and peak gain of-5.3dBi at60GHz. The BSIS-UC-EBG structure which can be considered as a frequency-selective surface (FSS) or high-impedance surface (HIS) is introduced to enhance the antenna performance. It is clear that the center frequency is about60GHz and the frequency band-gap lies between58-62.1GHz at which the reflection phase is between±90°. It is possible to broaden the impedance bandwidth through the helpful coupling to the radiator and the gain can be increased because of the constructive interference created by in-phase reflection from BSIS-UC-EBG. The layout of final antenna is composed of a rhombus radiator patch, two coplanar grounds, a50-Ω coplanar waveguide (CPW) feeding and a periodic IS-UC-EBG grid, which has an overall size of7x9mm2. It provides an impedance bandwidth of36.6%(49.3-71.4GHz) and peak gain of4.7dBi at60GHz. An enhancement in antenna bandwidth of16.4%and10-dB gain improvement from original patch are obtained.The research results provide instructions for the design and analysis of60GHz planar antenna with EBG structure. They also provide new ideas for the application of EBG structure on antennas. |
PDF Full Text Request