Q236 : Modelling Insulators in HIFREQ

Question
Is it possible to model insulators using HIFREQ?

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Answer
HIFREQ doesn't directly offer a model for an insulator. It is possible to use a conductor with a large resistivity as a model for an insulator, but this is subject to numerical problems and should be used with caution. On the other hand, the insulators have very little effect on the far fields and can simply be ignored in many cases.

Very close to the insulator, polarisation effects in the insulator may affect the normal component of the field (the component tangential to the insulator is not affected strongly). This is taken into account in HIFREQ, but in a way that makes it susceptible to numerical problems. This usually manifests itself as a very large condition number for the matrix. This affects the accuracy of the results.

If you choose to use this approach, you should check your results for the following message in the F09 file:

"The Hermitian matrix has a very large condition number. Check computed current distribution carefully."

If this message appears, the results computed by HIFREQ may not be very accurate. If this is the case, the best approach would be to use the field computed by HIFREQ in the absence of the insulators as the input of a package dedicated to the computation of the fields around dielectrics.

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