Modal Analysis of a Cylindrical Resonator Partially Filled with Dielectric

The interaction of resonant modes with a partially filled, radially distributed dielectric in a cylindrical resonator is investigated. In non-uniform filling configurations, the sensitivity of resonance-based dielectric evaluation depends strongly on the spatial overlap between the resonant electric field and the dielectric volume. The commonly used TM010 mode concentrates electric energy near the cavity axis, leading to weak interaction with off-axis dielectric samples. An alternative modal structure based on the TM110 mode is therefore examined in the X-band (8–12 GHz), where its off-axis electric-field localization provides substantially improved dielectric participation. Eigenmode analysis demonstrates that TM110 exhibits a 13-68% higher electric energy filling factor, and produces 1.4-4 times larger frequency shifts than TM010. Driven-port simulations further confirm that TM110 is more effectively excited, with a S11 ≈ -23 dB compared to S11 ≈ -18 dB for TM010.