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HFSS-Problem Assigning Symmetry Boundaries

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_skorpion_

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symmetry boundary

Hi all,
I have some problems when I try to simulate in HFSS a filter (that has a plane of symmetry) using the Symmetry Boundaries and I would like to know if you can help me.
I have looked in the HFSS online help and I am doing theses passes:

Assigning Symmetry Boundaries:
1. Select the object face to which you want to assign the symmetry boundary.
2. Click HFSS>Boundaries>Assign>Symmetry.
The Symmetry Boundary dialog box appears.
3. Type the boundary’s name in the Name text box or accept the default name.
4. Select the type of symmetry plane the boundary represents: Perfect E or Perfect H.
5. Click Impedance Multiplier.
If the design includes a port, you must adjust the impedance multiplier or the computed impedances will not be for the full structure.
The Port Impedance Multiplier dialog box appears.
6. Type a value in the Impedance Multiplier box, and then click OK.
7. Click OK.

I have simulated the complete filter (without the symmetry Boundary) but when I draw only half, I select the face (that is a plane of symmetry) and I use the impedance multiplier (2 to Perfect E or 0.5 to Perfect H) the result that I obtained is wrong (approximately 0).
Do you know which could be my problem? Should I draw the complete structure and then try to apply the symmetry boundary? Could you tell me something more about this option?

Many thanks in advance
 

shahid78

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symmetry plane in hfss

hi

well i havent used HFSS but through my experience with other 3D EM simulator i guess you need to model whole structure even if you use symmetry boundary conditions. because the purpose of symmetry boundary conditions is to reduce the simulation time as well as memery use as it need to calculate the fiels only in half space of your model
i hope this information is helpful to you

regards
 

_skorpion_

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symmetry in hfss

I will try it.
If anyone can confirm it please tell me.

thank you
 

_skorpion_

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hfss impedance symmetry

I continue with the problem.
I have tried to draw the full structure and do the same passes but I get a warning:
"The background does not fully touch the following boundaries 'Sym 1'. This may produce an incorrect result".

I continue without get the correct results. Anyone can help me?
 

moxiwen

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Re: hfss impedance symmetry

I continue with the problem.
I have tried to draw the full structure and do the same passes but I get a warning:
"The background does not fully touch the following boundaries 'Sym 1'. This may produce an incorrect result".

I continue without get the correct results. Anyone can help me?

Hi, I'm from china. The symmetry boundaries should obay 2 rules.
1.The symmetry plane should be exposed in the background.
2.The symmetry plane should define in plane, not curve.

I hope that this could be helpful...
 

reidintransit

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Re: hfss impedance symmetry

Hi, I'm from china. The symmetry boundaries should obay 2 rules.
1.The symmetry plane should be exposed in the background.
2.The symmetry plane should define in plane, not curve.

I hope that this could be helpful...

3. The symmetry plane should not cut through an object in the 3D modeler window. -From HFSS Help. so don't build whole design.
The symmetry boundaries are either perfect E or perfect H, make sure you are setting the right one. I suspect perfect E cutting through traces will short them together.
Try plotting the fields in the full model you have to see if the fields are actually symmetric where you want to place the symmetry boundary.
 
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