HFSS integration line doubts

[ptshao]

integration line port hfss

Hello, buddies:
Happy new year!!
I got some confusions on integration line assignment in a wave port. Please see the attached file. For File 1, I would like to obtain the port impedance of the folded dipole antenna, leading to the choice of a wave port which can facilitate solving a characteristic impedance. My aim is to solve the port impedance at 2.45GHz, so I tried to solve port only setup. When I connected two midpoints of two arms as the endpoints of an integration line, the port impedance varied much, let's say, from about 187 ohm to about 208 ohm, compared with the case without assignating an integration line. The problems are 1, Should I assign an integration line for a wave port? 2, What integration line are correct one for this case?

For File 2, I have no confidence about the settingup of the excitation assignment. I measured the impedance of this coplanar stripline(CPS) that is about 24 ohm(whatever from TDR or VNA measurement), but now from this simulation it appears about 85.5 ohm. So No.1, what's wrong with this? 2, Is the setting correct?

Thanks for your time!

 

[iamdrew]

room simulation in hfss

On your printed antenna, I would change a couple things. First, you need more room between the end of your antenna and any type of Radiation or PML boundary. Second, I would highly recommend a PML over the radiation, but that is your call. Third, I would add thickness to the metal, and then draw the integration line just between the two edges of the metal thickness (not from center to center as you have now). Maybe it was already thick, I didn't zoom in very far.

For your second problem, again, draw the integration line between the two metals, not from center to center. That should help out quite a bit.

Good Luck!

Added after 19 minutes:

I just sim'd your second structure, and it looks like it is ~85 ohms. Are you sure that you are sim'ing the same structure that you measured? It appears to be more of two coupled lines, or a slot mode instead of a coplanar structure. But maybe I am not looking at it correctly.

 

[ptshao]

hfss waveport integration line

Hi, buddies: I have solved the problems stated above.
Answer for Question1: Try to make a bigger waveport. Remember that there is less risk to make a larger waveport than to make a smaller or narrower waveport, because a smaller port might introduce higher order modes.

Answer for Question2: For microstriplines, in most cases, Zpi is enough for simulation, which means there is no need for an integration line. But if you care about slotlines or CPW, using integration lines are the preference to calculate Zpv.