近年来，无线收发系统的革命性发展对天线设计提出了迫切的创新需求。介质谐振天线由于其欧姆损耗低，结构设计灵活，工作模式丰富，辐射特性优良，近年来吸引了众多天线研究者的关注，未来必将在超宽带通信、卫星导航以及毫米波通信等领域得到广泛应用。本文以介质谐振天线模式理论为研究基础，多模式设计方法为研究重点。在归纳矩形和圆柱介质谐振天线常见基次模和高次模场分布的基础上，探寻如何利用介质谐振天线的多模式提升天线的电性能。首先，为增加天线极化形式，本文提出了两种多模介质谐振天线设计方案。一是提出一种利用双端口差分馈电激励两个基次正交模式的矩形介质谐振天线，该天线可辐射定向水平双极化波，在端口隔离，交叉极化和方向图对称性方面均具有优良特性。在此基础上增加新的端口，设计出一种三极化矩形介质谐振天线，增加了极化维度，为通信领域的极化分集问题提供一种新的方法。二是提出一种全向辐射的双极化天线设计方案，使得天线结构及馈电更为简单。其次，为了解决全向辐射天线低剖面与宽频带之间的矛盾，本文采用微带贴片作为馈电结构激励介质圆环，利用微带贴片的TM02模和介质圆环的TM01δ模这两种混合模式，设计一种低剖面全向辐射宽带天线。此外，研究利用介质连续径向多模式展宽天线带宽的方法，设计了一种工作于四种模式的圆环介质加载圆柱介质谐振天线，该天线具有宽频带低剖面特性，且频带内方向图较稳定。第三，在研究金属接地板对介质谐振天线辐射特性的影响的基础上，本文提出两种控制金属接地板对H面宽波束辐射特性影响的方法，一是给圆柱形全向辐射介质谐振天线增加金属反射板控制其辐射波束宽度和方向，二是通过减小并优化金属地板形状来扩展原有波束宽度。最后，本文设计了一种双频圆极化介质谐振天线阵列。该阵列采用一种双频双线极化矩形介质单元作为阵元，并利用连续旋转馈电方法构成圆极化，实现了同一个口径面内介质阵列的双频段工作，是一种面向实际应用的紧凑型天线阵列。
In Recent years, the revolutionary development of wireless transceiver systems has put forward urgent innovation demands for antenna designers. Due to low ohm loss, flexible design, various working modes and excellent radiation characteristics, dielectric resonator antennas have attracted the attention of many researchers, and will be widely employed in ultra-wideband communications, satellite navigations and millimeter-wave wireless communication systems.On the basis of mode theory, importance is attached to multi-mode design method. Concluded from the electromagnetic fields of basic and high modes of rectangular and cylinder DRAs, the enhancement of multi-mode performance is investigated as well.In the first place, different multi-mode DRAs are raised to increase polarization forms. A rectangular DRA is fed by a dual-port differential network to excite two orthogonal basic modes. In this case, directional horizontal dual-polarization can be realized, and port isolation, cross polarization and radiation patterns are well performed as well. In addition, a triple-polarized DRA is designed by adding another port, so the polarization diversity can be promoted. Aside from it, another DRA is designed with omnidirectional radiation patterns, and its feeding network is simpler.Subsequently, in order to solve the contradiction between the height and bandwidth of DRA, a low profile broadband omnidirectional DRA is proposed by combining TM02 mode of microstrip patch feeding structure and TM01δ of dielectric ring. In the meantime, the approach to widen the bandwidth by exciting multiple continuous working modes in radial direction is investigated as well. At the same time, a cylindrical dielectric resonator antenna loaded with an annular dielectric is designed by exciting four modes, and it owns wideband, low profile, and stable radiation patterns.Based on the investigation of influence of metal ground on DRAs radiation patterns, two methods are presented to control the H-plane radiation patterns. One is to modulate the beamwidth and direction through the addition of a metal reflected board, the other is to broaden beamwidth by optimizing the shape of the ground.Finally, a dual-frequency circular-polarized DRA array is designed. Dual-frequency dual-linear-polarized rectangular DRA is chosen as the element, and circular polarization is realized by continuous rotating feeding method. This compact array is a good candidate for practical application.
