HFSS Simulation

Hi,

I am using HFSS to simulate a coplanar microstrip lines. I am confused on what kinda port I gotta use,i.e lumped port or waveport. Also if my coplanar strip lines are terminated by a complex load(R,inductance or capactiance) will lumped port work out fine?.

Thanks for your help.

Hi,

You can use Waveport. However - you must make sure that it is not too wide nor too narrow (ha !).

1) The waveport must touch all grounds (two coplanar grounds, and in grounded CWG also touch the ground and the bottom (as in microstrip).
2) The waveport must no exceed lambda/2 in any dimention.
3) The waveport must not be too narrow - i.e. close to the strip in the middle.

The following is not necessary unless you think you did something wrong:
In order to check yourself do a ports only solution with 3 modes and make an interpolating sweep in your frequency range. Plot re(Gamma) and look for propagating modes that are because of the width of the port and not related to the CWG. re(Gamma) should be zero for propagating waves and positive for evanecent waves. You can click each port fields (in the project manager) and see the direction of the field lines for each mode. The only propagating mode should be where the lines are from the strip to the ground (at the sides). If the lines are from the port edges to all of the 3 strips (TE01) and the mode is propagating you need to change the width of the port.

This is described in Ansoft HFSS CWG training that is available online in www.ansoft.com (click support button and then training)

Regards,
Itai

Hi Itai,

I have coplanar strip line structure not CWG. I have a substrate and also the coupled lines are close to each other?. Can I still use the waveport?. If yes how can I define teh ports?

09

I think I answered somewhat in your other post:
https://www.edaboard.com/ftopic111818.html
You could use either one, wave or lumped port, but at your frequencies better to use wave ports.
The RLC elements can be included in simulation using a type of boundary condition, called, well ... Lumped RLC

Please post a picture of the subsection of your transmition line model.

Itai

Hi Itai ,

I have posted the details of my structure in the post "port definition in HFSS"