Scott: Thanks for your help as usual. Item 1/2/3 are pretty much covered. Item 4 is a surprise as I have so many email exchange with CST tech support and it has not been mentioned even once ! I'm re-running the simulation as we speak now. Regards Perry ======================================= Perry Qu Design & Qualification, Alcatel Canada 600 March Road, Ottawa ON, K2K 2E6 DID: 613-7846720 Fax: 613-5993642 Email: perry.qu@xxxxxxxxxxx ======================================= -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Scott McMorrow Sent: Tuesday, September 26, 2006 2:36 PM To: Perry.Qu@xxxxxxxxxxx Cc: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: Question for CST Microwave Studio experts 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 TeraspeedR 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 > > ======================================= > > > > > ------------------------------------------------------------------ > To unsubscribe from si-list: > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field > > or to administer your membership from a web page, go to: > //www.freelists.org/webpage/si-list > > For help: > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > > List FAQ wiki page is located at: > http://si-list.org/wiki/wiki.pl?Si-List_FAQ > > List technical documents are available at: > http://www.si-list.org > > List archives are viewable at: > //www.freelists.org/archives/si-list > or at our remote archives: > http://groups.yahoo.com/group/si-list/messages > Old (prior to June 6, 2001) list archives are viewable at: > http://www.qsl.net/wb6tpu > > > ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu