| In the wireless communication system,the antenna is an indispensable part.With the development of wireless communication system,antenna design technology is also continuously improved.The development trend of antenna is multi-band,broadband,multi-polarization,miniaturization and low profile.These factors need to be considered during the antenna design process.Miniaturized antenna has smaller size.Thinner and smaller antennas not only have lower manufacturing cost,but also have smaller wind resistance and can be installed more easily.Multi-band antenna can cover multiple frequency bands at the same time.Therefore,in a limited arrangement space,multi-band antenna can replace several antennas covering various operating bands.Multi-polarized antenna can deal with multipath fading problem and enhance signal reception quality.This thesis carried out research on how to realize antenna element multi-mode work and achieve miniaturized simultaneously.For this purpose,these following related working have been carried out.1.The working principle and design method of the artificial magnetic conductor unit have been introduced.The low-profile antenna has been theoretically analyzed.A dual-polarized antenna with compact structure,good impedance matching,directional radiation characteristics and low profile has been proposed.The role of the artificial magnetic conductor reflector in antenna miniaturization has been analyzed.Then the antenna has been fabricated and tested.And the distinction between measured and simulated results was within an acceptable range.The wideband dual-polarized trapped omnidirectional antenna was also studied.By loading or etching the SIR structures separately,the band notch characteristics of the antenna in both vertical and horizontal directions were achieved.2.Study on low-profile dual-polarization antenna MIMO array has been carried out.Feed network of MIMO array was designed.Decoupling methods for MIMO systems have been researched and analyzed.The T-shape decoupling branches has been theoretically analyzed.An improved MIMO array with a port isolation improvement of 10 d B or more has been designed.Then the MIMO array has been fabricated and tested.And the distinction between measured and simulated results was within an acceptable range.3.Research on dual-band low profile antennas has been carried out.Groove-shaped dual-band low-profile antenna and circular dual-band dual-polarized low-profile antenna have been proposed.Using the method of opening the gaps of different structures on the key positions of the classical AMC structure,the dual-band operating characteristics of the AMC unit has been achieved.Through the analysis of equivalent circuit,surface current,incident characteristics and reflector size,the working principle of the dual-band AMC reflector have been illustrated.Then the circular dual-band dual-polarized low-profile antenna has been fabricated and tested.And the distinction between measured and simulated results was within an acceptable range.At last,the performance of circular dual-band dual-polarized low-profile antenna has also been compared with previously published antennas. |
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