Study Of Electromagnetic Band Gap Structure And Its Application In Microstrip Antenna

The electromagnetic band gap structure has the characteristics of the electromagnetic band gap and the same phase reflection.Therefore,since it was put forward in 1987,after more than 10 years of rapid development,it has been successfully used in design of a high performance millimeter wave antenna,a filter,a resonator,and a high-performance amplifier.In this paper,the theory of EBG structure and the study of band gap characteristics are studied,and then the EBG structure is applied to the antenna design.The specific research contents are as follows:Firstly,main factors that influence the band gap characteristics of the EBG structure are analyzed in this paper.Primarily,four influences factors such as the thickness of the dielectric substrate,the metal patch area,the metal hole size,and the unit spacing are analyzed;then the influence from the EBG cell surface slots are studied;finally,not only the periodic EBG structure but also the aperiodic EBG structure is designed and its influencing factors are also analyzed.Secondly,a MIMO antenna based on a periodic EBG structure which can be used in WLAN is designed.The measured results show that compared with the traditional MIMO antenna,the relative bandwidth of the EBG antenna is increased by 34.9%,its gain is increased by 2.6 dB,and its backward radiation is reduced by 25 dB.Besides,in the whole working frequency range,its isolation(S₂₁)is less than-25 dB,and its cross polarization is less than-15 dB.Thirdly,a dual frequency microstrip antenna based on an aperiodic EBG structure is designed.Its two resonant frequencies are 4.9 GHz and 5.4 GHz respectively.The measured results show that compared with the traditional MIMO antenna,the relative bandwidth of the aperiodic EBG antenna has increased by 41%and 25.4%and its gain has increased 2.5 dB and 0.86 dB at two resonant frequencies respectively,with<-20 dB on its cross polarization.Finally,a MIMO antenna based on an aperiodic EBG structure is designed.The resonant frequency of the antenna is 5.75 GHz and 6.44 GHz.Compared with the traditional MIMO antenna,the measured relative bandwidth of the antenna is improved by 28.9%and 27.8%at two frequencies,respectively.And its peak gains are increased by 5 dB and 1.1 dB in two different resonant frequencies with<-20 dB isolation in the whole frequency band.