Analysis And Design Mechanisms Of Dielectric Resonator Antennas

Modern wireless devices keep raising increasingly complicated and strict requirements to antennas,e.g.,a)the miniaturization of wireless devices leads to the decrease of the available space for antennas;b)since more functions are integrated into one device,the available space for antennas is further compromised due to other modules;c)for extreme space utilization and from the aesthetic point of view,the platform for antennas grows irregular;d)although the external circumstance for antennas in devices becomes poorer,the antenna performance cannot be compromised.The above requirements urge researchers to customize more complex and powerful antennas.The dielectric resonator antenna(DRA)is famous for its excellent design freedom,abundant operating modes,and low loss,making it apply to systems requiring customized,integrated,and high-frequency antennas.Nevertheless,to develop basic physical insights and typical electromagnetic models for DRAs,classical DRA theory focuses on regularshaped dielectric blocks,such as rectangular,cylindrical,hemispherical,triangular,and elliptical ones,on a flat ground plane.On one hand,this boosts the development of DRAs.However,it also compromises their design freedom,performance diversity,and application scope.Hence,this dissertation aims to investigate irregular DRAs with flexible forms and improved performances.These DRAs have deformed shapes and contain more than one kind of material,which increases their diversity and complexity.As a result,classical DRA theory cannot directly provide insightful and applicable analysis and design methods for these DRAs.Meanwhile,investigation on irregular DRAs will help to develop deeper physical insights into these three-dimensional resonant dielectric antennas.Therefore,this dissertation focuses on the following studies.1.For basic irregular-shaped DRAs,i.e.,conformal DRAs on arc-shaped ground layers,their analytical modal theory is investigated.A set of composite boundary conditions is introduced,and the quasi-rigorous modal solution is derived accordingly.Next,the ground effect is studied,based on which a co-design strategy is proposed and then implemented through the surface integral equation-based substructure characteristic mode analysis(SIE-SCMA).Meanwhile,the superiority of SIE-SCMA in practical DRA problems is discussed.2.For basic composite DRAs,i.e.,stacked DRAs,their classical homogenization methods are re-evaluated.The flaws of the widely used effective capacitance models are discussed.Then,based on the effective medium theory and the resonance nature of DRAs,better homogenization approaches are proposed and tested.3.According to the Cartesian multipole theory,the resonance of DRAs in random shapes is studied from a novel perspective.This method quantitatively explains the transition in modal characteristics when a DRA undergoes structural deformation.The intrinsic difference between the resonant modes of regular and abnormal DRAs is revealed accordingly.Next,a novel DRA design method is proposed based on the Cartesian multipole analysis.A series of examples are presented.4.The idea of synthesizing sophisticated modes in irregular DRAs based on the required radiation performance is proposed.First,the relation and difference between the synthesized and classical DRA modes are discussed.Then,several irregular DRAs operating in artificial modes are proposed.These DRAs have abnormal shapes or contain multiple media to form an ultrawide radiated beam.The idea of mode synthesis is demonstrated accordingly.In this dissertation,the operating mechanisms of deformed and composite DRAs are further studied with the help of modal theory and multipole analysis.Accordingly,novel analysis and design methodologies for these DRAs are proposed;the difference between the resonant characteristics of traditional and these irregular DRAs are investigated in depth.To validate the applicability of the proposed methodology,a series of applicationoriented DRAs are developed for the first time.