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Port definition in HFSS 9

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DLHDLH

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hfss port

Thanks for reading this! I have a problem with definining a port in HFSS 9.2. My intend is to just understand this program for the first time. The example I want to simulate is a simple 50 Ohm microstrip line of a certain lenght. Top layer is the strip (PEC), than a substrate (some Rogers epsr=2.2) and a groundplane (PEC) on the bottom. All layers have the same length, so all front faces are in the same plane. Around it all, with a little distance, I put a vacuum cuboid defining five faces of it as radiation boundary (RAD1) and the bottom face as perfect E with infinit groundplane. I want to excite the microstrip on one side and leave the other one open to see the caracteristic maxima & minima in the S11-plot. To define a waveport, I selected the front face of the strip and of the groudplane. I choose "assign excitation" and defined a "new line" straight drom the lower edge fof the strip front face to the upper edge of the groundplane front face. It says that it is valid. Now I simulated within a wide range of frequency 1-10GHz. The lenght of the strip was choosen the way that I have to see maxim & minima of the open line. But that is not the case. I can plot a XY-graph of S11 but it not at all behaves as expected. I get a S11-paramteter around -0.00001 dB. I tried the same with a lumped port but it tells me: [error] Port refinement, process abc3d : "LumpPort1" is incorrectly set up. A gap source will be short circuited by conductors. I went through manuals and available workshop pages, but didn't really find a satisfying answer. Who knows what is wrong and probably could tell me how to it right. I want to understand that!
Thanks so much everybody!

I attached my file.
 

asdfaaa

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stripline hfss

DLHDLH said:
To define a waveport, I selected the front face of the strip and of the groudplane. I choose "assign excitation" and defined a "new line" straight drom the lower edge fof the strip front face to the upper edge of the groundplane front face.
You didn't properly setup the waveport if I understand you correctly. To define the waveport, you need define one 2-D rectangle(or circle, coaxial) shape, and then assign it to waveport.
For better understanding of the waveport, you may treat the waveport is just the cross section of one infinitely lone waveguid which is used to excite your structure,
HFSS will call one 2-D eigenvalue solver to get all the eigen mode in this waveguide first (where the eigen mode is the excitation on the waveport with respect to different mode), and proceed to the simulation. Therefore, there are some rules for defining the waveport. Pls refer HFSS help file.

Regards,
 

mwmmboy

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port hfss

There is a chapter on the help manual that explain the rules of thumb for this topic.

Hope this can help.

Bye
 

burton

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port round it defenition

It seems that the results you got is right, because you simulated a section of open-end microstrip
 

ryfnjust

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waveport edges perfect e

yes, burton is right i think
 

cvenkat

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hfss port

asdfaa is rite
 

anmin

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s11 for an open single transmission line is 0dB, because all energy is reflected. so you got it right.
 

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