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HFSS giving wrong solutions half the time

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Newbie level 5
Mar 31, 2009
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I've used hfss to simulate an on-chip inductive coupling link at 433MHz. Everything was perfect and the results were close to the values I got from ASITIC. I saved separation as a design parameter and changed that from 1cm-10cm accordingly and everything looked fine in 3D view.However, when I changed the coil separation from 1cm to 10cm, it gave me a wrong answer with negative resistance and mH(!) inductance values. Can anyone tell me if he has similar experience

What are you getting for seperation of 2cm, 5cm ?
How much deviation is there?

Need to check step by step.


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with an airvolume width of 2cm:

separation = 0.5cm ->OK
separation = 1.5cm ->OK
separation = 4.5cm ->Does not even simulate, it encounters some problem while meshing and says it might be because of skewed thin surfaces

Increasing airvolume width to 1meter does not help at all

Can you upload the project.
so that we can check.

Without understanding project it will not be correct to comment on error.

OK, now it doesn't simulate at all. Can you tell me how I can overcome the following:

"Surface Recovery failure Possible reasons : (1) . model has multiple objects with thin layers (2) complex model with object overlapping (3)" True surfaces are skewed "


This sounds like geometry fault,
How you are changing your width or spacing?
I dont know how your geometry looks like, but I think you have not created geometry with proper operations such as subtraction or uniting objects etc.

Try creating the geometry by different method and simulate.

Best of luck.


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My geometry consists of two thin-sheet coils(mm-sized) buried in dielectrics that are separated far from each other(1cm+).

I tried specifying some mesh operations to help it in meshing the structure, but it still gave me the same error.

Please email me your file, I will try to find out.


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