Improvement of Microwave Dielectric Resonators by Its Segmentation and Resultant Gaps

如果将介质谐振器垂直于电场进行分割，则介质损耗将减小，因为电能集中在缝隙中，导致空载Q值增大，但同时谐振频率增加。我们试图利用这些特性来改善微波带通滤波器的基本特性。对所需模式的应用降低了传输手的传输损耗，而对不想要模式的应用将改善寄生特性，因为所需模式不会明显改变谐振频率。我们通过电磁场模拟对这些可能性进行了详细的研究，并通过实验证实了这一点。其次，用于小型化和改善谐振器散热的镜像谐振器结构由于接触金属屏蔽处涡流的增加而降低了Q值。我们的建议是在谐振器和金属屏蔽体之间引入气隙，成功地减少了涡流，降低了介质损耗。事实上，7000的退化Q值被恢复到13000。在基于上述结果制作高质量的带通滤波器的同时，我们发现了控制想要/不想要的模的耦合系数的重要性，并将我们的计划扩展到耦合系数的物理研究。基于耦合模理论，我们得到了各种表达式，包括谐振器之间的能量交换周期、电场和磁场的重叠积分之差、介质谐振器中偶极矩的激发以及电和磁的消逝能量之差。我们将能够控制带通滤波器中相邻谐振器之间的耦合系数，从而实现改进的特性。

If one divides a dielectric resonator perpendicularly to the electric field, the dielectric loss will decrease, because the electric energy concentrates in the gap, resulting in a augmented unloaded Q. But the resonant frequency increases at the same time. We have tried to improve the basic characteristic of microwave band pass filters (BPFs) by use of these properties. Its application to the desired mode decreases the transmission loss of the pass hand, while that to the unwanted modes will improve the spurious characteristics because the desired mode dees not change the resonant frequency appreciably We studied those possibilities in detail by the EM simulation and confirmed it by experiments.Secondly, the image resonator configuration meant for miniaturization and improvement of heat dissipation of a resonator is known to degrade its Q value due to the increased eddy current on the contacting metal shield. Our proposal is to introduce the air gap between the resonator and metal shield, and has succeeded to reduce the eddy current less as well as the dielectric loss. In fact, the degraded Q of 7000 was recovered to be 13000.While we were tying to fabricate a high-quality BPF on the basis of the results above, we found the importance of the control of coupling coefficient of both the wanted/unwanted modes and extended our plan to the study of physics of coupling coefficients. Based on the coupled mode theory, we found a variety of expressions, including the period of energy exchange between resonators, the difference of overlap integral of the electric and magnetic fields respectively, excitation of dipole moment in the dielectric resonator and the difference of electric and magnetic evanescent energies. We will be able to control the coupling coefficient between adjacent resonators in a BPF so as to realize the improved characteristics.