Calculating the Q of a Resonant Cavity

Description

This recipe permits you to calculate the Q in a homogeneous dielectric-filled cavity with uniform wall losses, using the equation:

where s is skin depth, tgis dielectric loss tangent, n is the surface normal for the cavity wall faces, and and represent wall surface area and cavity volume, respectively.

Usage Examples

To calculate the Q of an air- or solid-dielectric filled cavity, fed with a below-cutoff port aperture, or obtained via an eigen solution.

Prerequisites

The Object (or Object List) representing the cavity total volume must already exist, as must the Face List corresponding to the total wall surface area of the cavity. You can create both via the Modeler menu. The solution should be tuned to the desired resonant frequency for evaluation.



The above equation is only valid for cavities filled with one dielectric material across the entire volume. For cavities with different dielectric fills (e.g., a dielectric resonator within a larger metal cavity), dielectric loss must be evaluated using integration by parts for each dielectric material volume. The equation also assumes the same conductivity for all walls, and no nonreciprocal (e.g., ferrite) property to either walls or fill.