Eigenfrequency Calculations
When making eigenfrequency calculations, there are a few important things to note:
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Nonlinear eigenvalue problems appear for impedance boundary conditions with nonzero conductivity and for scattering boundary conditions adjacent to domains with nonzero conductivity. Such problems have to be treated specially.
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Some of the boundary conditions, such as the surface current density condition and the electric field condition, can specify a source in the eigenvalue problem. These conditions are available as a general tool to specify arbitrary expressions between the H field and the E field. Avoid specifying solution-independent sources for these conditions because the eigenvalue solver ignores them anyway.
Using the default parameters for the eigenfrequency study, it might find a large number of false eigenfrequencies, which are almost zero. This is a known consequence of using vector elements. To avoid these eigenfrequencies, change the parameters for the eigenvalue solver in the Study Settings. Adjust the settings so that the solver searches for eigenfrequencies closer to the lowest eigenfrequency than to zero.