Polarisation with HFSS

Everything. Some parts are much harder to get to than others. Ask Ansys to add a feature to extract rotating linear polarization, it should have been there years ago. Maybe if enough of us ask it will actually happen.

I often find myself discussing polarization issues with the Ansys AE's as it is not a trivial issue. I find "total realized gain" to be most useful and often compare it to the polarization that I think I have (and want) in a particular antenna. Ludwig's article might be helpful too. They cite in in the on-line-help sections on polarization.

Stutzman wrote a book on the subject if you really want to look deeply into the details.

How is "total realized gain" related to the polarisation?

I think of it as a pattern where the polarization at each point is adjusted to match the polarazition to each far field direction. This is the best one could ever do with a pattern. I find it useful to access how close to "perfect" a particular antenna is performing. The polarization will generally be different over the field of view for any antenna.

Total realized gain radiation pattern doesn't tell you much about the polarization, since it includes all polarizations (your antenna is most probably not perfect, so you might have not only the desired RHCP, but also the undesired LHCP). You must select a specific component to plot the radiation pattern for a specific polarization (i.e. X, Y, Z or LHCP, RHCP)...

With what parameter can I check if an antenna is linear polarised?
And what can I use to determine circular polarisation?

If you are able to plot the phase of two orthogonal polarizations (for example E(theta) and E(phi) ), phase difference should be zero (or -180) for pure linear polarization. For circular polarization, orthogonal E-field strengths should be same, phase difference should be - or + 90 degrees.

What does the axial ratio, the polarization ratio (LHCP, RHCP, SpericalPhi or SpericalTheta) and the Ludwig-3 describe about the polarization?