hfss coupler

Hey, I'm wondering if anyone can give me some hints, tips, or pointers on simulating a directional coupler (3dB Quadrature Hybrid). We've run simulations in other programs (MWO) with good values, but more indepth solutions are required and I'm not very familiar with HFSS.

What results are you looking to get from HFSS?

a) Be sure to check the current distribution. Se my posts in:

https://www.edaboard.com/viewtopic.p...680&highlight=

b) Do a convergence analysis by comparing s-parameters of runs with decreasing Delta-S error tolerance AND port error tolerance (if using wave ports). Do this in MWO also by increasing mesh density.

c) Don't forget to re-normalize wave ports to 50 ohms.

d) Since MWO is a shielded MOM simulator try using the same size HFSS enclosure with PEC walls. Of course also do it with radiation boundry.

You can use a *.tech file to map MWO GDSII files into HFSS. This will save from having to re-draw artwork. Here are instructions on getting it to work and an example attachment:

Attached is an example in MWO using a two layer substrate.

Here are the steps.

1) In MWO under options, drawing layers, you must add a new GDSII export mapping. Call it HFSS. Set the layers you want to export and take note of the GDSII layer number.
2) Export layout using HFSS GDSII flat.
3) Create a .tech file for HFSS to read. The units are in nm. See my example for a 20 mil board. As of HFSS v9 the colors still do not work (have not tried v10 yet).
4) Import into HFSS and set the units to mils (do not rescale).
5) Clean up by assigning colors, materials, and merging as necessary.
6) Add ports, boundries, etc.

Also, I had to make the vias square since HFSS did not import a round via (not sure why).