| 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 has two unique properties:in-phase reflection band gap and forbidden band gap.For forbidden band gap characteristics,the S parameter curve and dispersion curve were analyzed.What's more,the reflection phase curves were mainly analyzed for the reflection phase characteristics.This paper mainly aimed at UC-EBG,designed a new type of EBG structure and applied EBG structure to improve the gain of the antenna and broadens its bandwidth.First of all,a UC-EBG structure and its design method were studied.The new type spiral center symmetry structure was constituted by the translation and rotation of rectangular.The substrate was made of FR4 with the different thickness,a relative dielectric constant of 4.4 and dielectric loss of 0.02.When the thickness of the substrate was 2.0 mm and 1.8 mm and 1.6 mm,there were two reflection band gaps;When the thickness of the substrate was 1.4mm and 1.2mm,only one band gap was obtained.And the bandwidth with the thickness of 1.2mm was highest.The bandwidth would increase with the reduction of substrate thickness and width.And along with the increase of relative dielectric constant of the substrate,the bandwidth would move to low frequency.Secondly,two methods were proposed to broaden the bandwidth of monopole ultrawideband(UWB)antenna in this paper.The traditional antenna has a bandwidth of 8.11GHz.With iteration holes added to the radiation patch,the bandwidth of antenna can be extended to 9.23GHz.Thereafter,by loading rectangular patches on both sides of the feedline,the bandwidth of antenna can further be expanded to 10.24GHz.The largest impedance bandwidth of 174%can be obtained.Then,the antenna with the circular hole are studied with miniaturization.By using the basic structure of Archimedes spiral,the size of the feedline were greatly reduced.The antenna's miniaturization size of 50×40mm2 was obtained,while the traditional antenna's size is 115×60mm2.The miniaturization antenna performed better in low frequency band.Moreover,the gain and the radiation patterns were discussed.The designed antenna had a simple planar structure which was easy to fabricate.The correctness of simulation results could be verified by measured results.Finally,this paper described a concentric rectangular rings(CRR)electromagnetic bandgap(EBG)structure.And the reflection phase of the CRR-EBG was also studied.The CRR-EBG structure was applied to a circular patch microstrip antenna(CPMA).The bandwidth of the CPMA can be broadened by 70MHz,while the gain of the antenna can be improved to 7.29dB.And the resonance point moved to the lower frequency,while the volume of the antennas kept original sizes,which meant the CPMA achieves miniaturization in a certain degree.The CRR-EBG was also used to a penta-band coplanar waveguide antenna(PBCWA).The way could effectively reduce the return loss of the antenna at the resonant frequency point which indicated that the antenna had the better impedance match characteristic.And the gain of some of the resonance point were improved.The research results would provide reference for the design and analysis of the microstrip planar antenna with EBG structure.And all the processes also would provide new ideas for the application of EBG structure on antenna. |
PDF Full Text Request