courcirc8
Junior Member level 1
hfss cap
I am using HFSS to extract some portions of my VCO tank.
The model of inter-digited capacitor I got from HFSS had a suspicious high value (190f and I was expecting 110f)
So i build a very simple test case: 2 plates of 10um*10um separated by 1um of oxyde (Er=3.9).
Everything is inside a vacuum box. I use lumped ports and driven terminal solution type.
If you apply the formula of the planar capacitor, you expect something around 3.45ff
I got 6ff from HFSS!!!
My extraction is at 10GHz to I expect HFSS to have problem with small geometries at this freq, but increasing the freq doesn't help so much...
Am I doing something stupid?
Please help, this test case makes me mad!
___________________________________________________________________________
I think I got part of the explanation...
The size of my cap is very small compared to the lambda, so the automatic meshing doesn't work really well here.... With 2 thin plates, HFSS generates "Failed to solve due to lack of precision"
I was using previously a big second plate, because I was trying to represent something over the substrate.
The problem is how can I solve this very simple case with enough precision? And will it work for more complex structures? If I can generate a small mesh manually, I will not be able to use It to model my 6 metal stacked (serial/parallel) inductor? I don't have 100Gb of memory available for that!
NB. I use Zo=1000 to avoid having S11=0.000000....
Somebody uses HFSS to extract metal-metal cap?
Any ideay?
Many thanks,
Eric
I am using HFSS to extract some portions of my VCO tank.
The model of inter-digited capacitor I got from HFSS had a suspicious high value (190f and I was expecting 110f)
So i build a very simple test case: 2 plates of 10um*10um separated by 1um of oxyde (Er=3.9).
Everything is inside a vacuum box. I use lumped ports and driven terminal solution type.
If you apply the formula of the planar capacitor, you expect something around 3.45ff
I got 6ff from HFSS!!!
My extraction is at 10GHz to I expect HFSS to have problem with small geometries at this freq, but increasing the freq doesn't help so much...
Am I doing something stupid?
Please help, this test case makes me mad!
___________________________________________________________________________
I think I got part of the explanation...
The size of my cap is very small compared to the lambda, so the automatic meshing doesn't work really well here.... With 2 thin plates, HFSS generates "Failed to solve due to lack of precision"
I was using previously a big second plate, because I was trying to represent something over the substrate.
The problem is how can I solve this very simple case with enough precision? And will it work for more complex structures? If I can generate a small mesh manually, I will not be able to use It to model my 6 metal stacked (serial/parallel) inductor? I don't have 100Gb of memory available for that!
NB. I use Zo=1000 to avoid having S11=0.000000....
Somebody uses HFSS to extract metal-metal cap?
Any ideay?
Many thanks,
Eric