Design Of High-Performance Dielectric Resonator Antennas

With the diverse quick development of wireless communication systems,higher and higher performance index requirements have been put forward for the antenna as their key component.Dielectric resonator antennas（DRAs）radiate electromagnetic waves based on the dielectric materials,and this kind of antenna has many advantages such as high radiation efficiency,low loss,and high design freedom,making the DRA suitable for high-performance wireless communication systems at this stage.Therefore,how to design dielectric resonator antennas with different characteristics is very challenging,and of high research value at the same time.After investigating domestic and foreign literature in recent years,we found that the principle and design of wide beam DRAs,wideband differential-fed DRAs,and low-profile wideband DRAs are still of great research value.Based on the above analyses,this thesis aims at designing some novel high-performance DRAs,in which three novel DRAs with wide-beam,wideband differential-fed,and low-profile wideband characteristics are designed and implemented respectively,and their design principles are analyzed in detail.The main contributions of the thesis can be summarized as follows.1.A wide-beam DRA is proposed,and both E-plane and H-plane half-power beamwidths（HPBWs）of the DRA are enhanced simultaneously.The proposed antenna achieves good wide-beam performance.First,based on the internal field distribution of rectangular DRA,an equivalent magnetic current model for analyzing the far-field pattern of the antenna is proposed.By using this model,the influence of the radiation intensity variations of various surfaces on the DRA radiation field is analyzed,and it is found that increasing the ratio of radiation intensity in the DRA top to that in its sidewall can broaden HPBWs of the antenna.Based on this principle,the E-plane beamwidth is increased by engraving a groove on the top of the dielectric resonator.Then,by loading a comb-like metal wall around the DRA,both E-plane and H-plane HPBWs of the antenna are further broadened.The currents on the comb-like metal wall are simulated,and the beam broadening principle that radiation interactions of the induced currents in different directions improve the antenna gains at low elevation angles is revealed.In addition,key parameters of the antenna are analyzed to investigate their influence on its HPBWs.Finally,the proposed antenna is fabricated and measured.The measured results show that the antenna has an-10 dB reflection coefficient bandwidth of 38.2%（2.58-3.8 GHz）,and its E-plane and H-plane HPBWs are 248°and 148°,respectively.2.A differential-fed wideband DRA is proposed,which achieves a wide impedance bandwidth and stable gains.First,based on the current and electromagnetic field distribution of the differential-fed structure,higher-order modes of the DRA that can be used to broaden its impedance bandwidth are screened out.Then,the relationship between resonant frequencies of the higher-order modes and the profile of the DRA is analyzed.TE₁₁₃ mode and TE mode can be excited simultaneously to greatly expand the impedance bandwidth of the proposed antenna.By engraving walls on the sidewalls of a rectangular DRA,its Q factor is reduced,making the resonant frequencies of these two modes closer to each other,and the broadband gains remain stable.In addition,a broadband feeding network with a differential signal is designed for the antenna.Finally,the proposed antenna is fabricated and measured,which shows a measured-10 dB reflection coefficient bandwidth of 53.9%（3.10-5.39 GHz）,with a measured flat gain performance from 5.5 to 7.4 dBi.3.A low-profile wideband DRA is proposed,which achieves a wider impedance bandwidth with a lower profile.First,fundamental mode TE₁₁₁ and higher-order mode TE₁₃₁ of the antenna are excited by the stacked structure,as the basis for the antenna broadband design.Then,the electric field distributions of fundamental mode TE₁₁₁ and higher-order mode TE₁₃₁ are compared.It is found that electric field magnitudes of the higher-order mode are much greater than those of the fundamental mode at the edge of DRA.Thus,by perturbating the DRA edge structure,the resonant frequency of the high-order mode can be adjusted.By loading the dielectric substrates with higher relative dielectric permittivity at the DRA edge,the resonant frequency of the higher-order mode is further reduced without changing the resonant frequency of the fundamental mode,and the antenna impedance bandwidth is widened by merging the resonant frequencies of these two modes.Finally,the performance of the antenna is simulated and analyzed.The simulation results show that-10 dB reflection coefficient bandwidth of the antenna covers 4.34-6.81 GHz frequency band,its relative bandwidth reaches 44.3%,and its maximum gain is 9.78 dBi.