Resonant and normal modes behavioral studies of shielded dielectric spherical shell resonator

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Electromagnetic theory has been used to derive characteristic equations for the shielded dielectric spherical shell resonator with a concentric metallic sphere at the center. Expressions for the quality factors have also been derived. Using these expressions for the characteristic equations and quality factors numerical computations have been carried out for the resonant frequencies and the quality factors for the TEnmℓ and TMnmℓ modes using numerical methods. It is found that as the outer radius b of the shielded dielectric spherical shell resonator is increases, the resonant frequency for a given mode decreases. It has also been observed that the quality factor increases as the outer radius b of the dielectric resonator increases. As a result of high quality factor there is fractional increase in the energy stored in the dielectric sphere is more compared to the fractional increase in the total power loss through the metal surfaces and the dielectric volume, which improves the spectral characteristics.