Research On Compact Antennas Based On Near-field Resonant Coupling Principle

With the rapid development of wireless communication systems towards high-level integration,the research of miniaturized and compact antennas becomes more and more important and has been a research focus in recent years.Compared with traditional methods to realise antenna miniaturization by loading resistances,reactances,dielectrics,meanderlines,slot gaps,shorting probes or posts,the advantage to realize the high-level miniaturization is unique by the near-field resonant coupling principle.The excellent impedance matching with signal sources can be obtained without external matching networks.Moreover,the antennas have high radiation efficiency.In view of the specific problem in the compact antenna design,this thesis aims to explore new ideas and methods for this kind of antenna designs on the basis of the near-field resonant coupling principle.Furthermore,the near-field resonant coupling technology and Huygens source antenna design principle will be organically combined in designing high-performance and miniaturized antennas.Besides,the proposed near-field resonant coupling technology will be utilized to design dual-band antennas and the UWB antennas with band-notched filters.Consequently,the proposed technology has enriched the miniaturized and compact antenna design methodology.Firstly,the thesis introduces the research background and significance as well as the recent study progress of the near-field resonant coupling principle and mininature antennas.Then,the basic antenna design concept is briefly illustrated.The related key performance parameters are introduced,such as impedance matching and radiation charateristics.The relationship among the above performance parameters is also introduced.Next,two electrically small,low-profile Huygens source antennas with broadside radiation performance characteristics are designed.The analysis of frontward radiating antenna model is demonstrated to explain the operational mechanism and design procedure.Likewise,the analysis of backward radiating antenna model is utilized to illustrate the way to improve the radiation efficiency.Furthermore,a dual-band patch antenna based on split ring resonator(SRR)is proposed.Due to the near-field coupling between the radiation patch and the SRR,the electric resonance could create a new operational frequency band much lower than the patch's fundamental mode and also dramatically improve the patch impedance bandwidth by the third harmonic resonance mode of the SRR element.The proposed antenna possesses exellent dual-band radiation performance characteristics including high radiation efficiency and stable broadside radiation performance.Finally,the near-field resonant coupling principle is applied to construct a UWB antenna with two continuously tunable,independent band-notches.Two band-notches are designed according to different operaitonal mechanisms to achieve low mutual coupling.By means of varactor diodes,the continuous tuning property is accomplished successfully.The realization of the above three antennas demonstrates that the near-field resonant coupling technology has great potential and significance in the field of improving the radiation performance of compact antennas and designing multi-functional antennas in the future.