简述了用于分析多胞超导射频腔场平坦度调节的微扰理论，推导了场平坦度的理论计算方法。针对超导腔微小范围内的纵向拉伸/挤压，进行理论计算分析与结构-电磁多物理场模拟计算以求得变形前后腔体场平坦度及其变化趋势，所得结果表明：理论分析结果与仿真计算结果基本一致，进一步深入验证了该微扰理论的有效性。在多胞超导射频腔的加工制造、运行过程中的关键环节，国际上广泛采用的两种方法——包括预调谐过程中的“先单胞后整腔”和运行时腔体调谐过程中“整腔拉伸/挤压”方法，基于分析结果，这两种方法正确性和合理性均在理论上得以验证。在超导射频腔腔型设计的第一阶段——单胞优化设计过程中加入结构-电磁多物理场分析，可使腔型优化设计过程更加高效，结果表明：优化后的单胞（包括端胞和中间胞）的频率敏感度应尽可能接近或相等，以保证在腔变形期间始终保持较好的场平坦度。

We introduce a formalism, inspired on the perturbation theory for nearly free electrons in a solid-state crystal, to describe the resonances in optical ring resonators subjected to a perturbation in their dielectric profile. We find that, for small perturbations, degenerate resonant modes are split with the splitting proportional to one specific coefficient of the Fourier expansion of the perturbation. We also find an expected asymmetry in the linewidths (and Q factors) of the split modes. Experimental transmission spectra from rings with specially designed perturbations show a qualitative match with the formalism predictions.