Control of the resonance frequency of microwave cavities is of great interest in many applications such as sensing and wavelength filtering. However, this task normally relies on active control via functional materials (i.e., polymers and ferrites, or a combination of both) excited by an external electric or magnetic field. In this article, instead, we propose an innovative whispering gallery mode cavity resonator with tunable bandwidth for sensing and wavelength filtering applications. The proposed approach exploits Fano-type resonances (FTRs) to improve the cavity performance in the microwave regime. We have measured a ~74% increase in the loaded quality factor compared to regular ring cavities, with only 1.9-dB additional loss. In addition, by carefully choosing the size of the transmitting and receiving monopole antennas placed inside the cavity and their relative angular spacing, we can easily tune the cavity response. The extra degree-of-freedom introduced by such variable angular spacing, responsible for the onset of FTRs, allows the cavity quality factor $Q$ to be continuously tuned from 385 to 670.

中文翻译：

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Fano辅助可调 X带微波环形谐振器

在许多应用中，例如传感和波长滤波，对微波腔谐振频率的控制非常重要。但是，该任务通常依赖于通过功能材料（即聚合物和铁氧体，或两者的组合）的主动控制，这些功能材料由外部电场或磁场激发。相反，在本文中，我们提出了一种创新的耳语回音壁模式腔谐振器，该谐振器具有可调带宽，适用于传感和波长滤波应用。所提出的方法利用了Fano型共振（FTR）来改善微波状态下的腔性能。与常规的环形腔相比，我们测得的负载品质因数提高了约74％，而附加损耗仅为1.9dB。此外，通过仔细选择放置在腔体内的发射和接收单极天线的尺寸及其相对角间距，我们可以轻松地调整腔体响应。这种可变的角度间隔所引起的额外自由度，导致FTR的出现，使得模腔品质因数得以提高 $ Q $ 可以从385连续调到670。