[SI-LIST] Re: Question for CST Microwave Studio experts
- From: Scott McMorrow <scott@xxxxxxxxxxxxx>
- To: perry.qu@xxxxxxxxxxx
- Date: Tue, 26 Sep 2006 14:36:12 -0400
Perry
1) Make sure that your waveguide port is significantly larger than the
microstrip, and contacts your ground plane.
2) Use the multipin option and define a pin at the center of the microstrip.
3) When you set up your mesh, be sure to have at least two mesh boxes
between the plane and the microstrip, one mesh box to cover the height
of the ground plane, and at least three mesh boxes encompassing the
width of the microstrip.
4) In your transient solver parameters dialog, check "Inhomogeneous port
accuracy enhancement"
The 4rd item is the most important, since microstrip is inhomogeneous.
Regards,
Scott
Scott McMorrow
Teraspeed Consulting Group LLC
121 North River Drive
Narragansett, RI 02882
(401) 284-1827 Business
(401) 284-1840 Fax
http://www.teraspeed.com
Teraspeed® is the registered service mark of
Teraspeed Consulting Group LLC
Perry Qu wrote:
> Hi,
>
> We are evaluating CST MWS recently and I'm having some issues with the
> waveguide port solutions. Set up a simple differential through via
> (microstrip on top layer of PCB to microstrip on bottom, no stubs) and try
> to study the impact of antipad clearance on the differential return loss and
> insertion loss. Using waveguide port and multipin definition, I got the
> differential insertion loss and return loss. The insertion loss curve looks
> rather wield, as I have -0.7dB loss from DC to about 4GHz, but then it
> climbs up to -0.4 dB from 4 to 10 GHz. I can't explain why I have higher
> insertion loss at low frequency. Single-ended S parameter computed from the
> mixed model results show the same trend.
>
> Using the exact same model but replace waveguide ports with discrete port
> and re-run the same simulation. The resulted single-ended insertion loss
> makes sense where I have a nice slope with very small insertion loss at low
> frequency and increase linearly as frequency goes higher.
>
> I had a few email exchange with CST tech support but I have not received a
> good explanation. I was wondering if any users here on the list have similar
> problem ?
>
> Thanks
>
> Perry
>
> =======================================
>
> Perry Qu
>
> Design & Qualification, Alcatel Canada
>
> 600 March Road, Ottawa ON, K2K 2E6
>
> DID: 613-7846720 Fax: 613-5993642
>
> Email: perry.qu@xxxxxxxxxxx
>
> =======================================
>
>
>
>
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