Learning Forum

[GeorgM]

I want to have all the radiated field of an antenna turned into an incident wave. An obvious way would be to place a perfect E sphere around the antenna. But this doesn't do the job as perfect E (and H) boundaries change the rotation sense for circular waves. So the backscattered wave is different from the incident wave and this is not what I want.

I could save the far field in a *.ffd file. But I see no way for the reversal as there is no H in this file. It seems to be always outgoing.

For the near field this might be easier. I can save the (radiating) near field on a sphere surrounding my antenna in an *.nfd file. Then I calculate E:=conj(E) and H:=-conj(H) with some hand written script and then create a *.nfd file with the new data. This is now the reverted field. Then I take this file as "external link" near field excitation.

Are there smarter ways to do this? Can I revert the field without the cumbersome way over manipulated *.nfd files? Is it possible to revert the far field in a similar way and use it as excitation?

Thanks

[AndyJP]

revert? Ah.. I was trying to comprehend what you want to reach... are you speaking about reverting the Poynting vector in the captured data file? Thinking about that, probably some matlab scripting is required. still don't get why it is needed, but anyway, it is not an object of manipulation in the field calc.

[GeorgM]

Yes, I want to revert the Poynting vector. But in such a way, that a RHCP wave remains RHCP (and vice versa) and doesn't change the rotation sense. This cannot be done with perfect E or H. In addition, the sphere would have to be aligned perfectly to the wave front.
The purpose is a longer story. I want to define a figure of merit for UWB antennas. It should reflect the similarity between the radiated pulse and the input pulse. This similarity is usually different in every direction. But I want a single number for the whole antenna in order to have some parameter for optimization.

[Praneeth]

I am not sure if this helps or not. Did you try using the field calculator?
It is possible to import the far field data as a source into HFSS. There you can make use of field calculator to extract the resulting fields.
Best regards.

[AndyJP]

isn't the field calc a postprocessing layer? And it can not be applied when exporting. So I do not see a way to use it for the purpose defined. correct me if I am mistaken.