Celine, If you are measuring things at or near 50 ohms and the test fixture and the thing being measured will not resonate, think about the wavelength of the highest frequency you want to evaluate and keep the length of the test fixture to 1/20 or less. If you want to make a better measurement, use 1/100. For example if you are working to 1GHz (Wavelength of 300mm) anything around 3 mm should be measured and removed from the measurement. If you are measuring things that can resonate in the frequency band of interest, then it gets tricky. You have to figure out what parasitic impedances can get in the way of the measurement. For example, if you are measuring the capacitance of an inter layer plane (Power plane to Ground plane capacitance) that is 10 nF and you have a via to that plane that is 75 microns long. You need to remove the via from the measurement. This is assuming you want to evaluate the capacitance of the VDD to Ground Plane and not what a chip will see at the surface. If you are trying to measure the capacitance of the inner layer, you need to conceder where the test setup will resonate. The inductance of a 75 micron via (3 Mils) is near (0.075 mm * 600 pH per mm) 45 pH. This structure will resonate at 1/(2 PI Square Root (LC)). That is 1/(2 PI Square Root (45 pH * 10 nF) or 237 MHz.=20 If you want to evaluate what a chip will see at the surface of the board with a single via, you don't remove the via because that is what you want to evaluate. What you do is port extend to the surface of the board. Use a shorted connector of the same type as on the board to find the electrical length of the distance from the calibration plane to the surface of the board. Best regards, John -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Xilei Liu Sent: Monday, June 26, 2006 6:34 AM To: dgun@xxxxxxxxxx; travissellis@xxxxxxxxx; si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: S-parameter passivity... Interpreting the results. Will it help if all the adapters lengths are considered in the calibration=20 procedure such that the calibrtion plane is brought to the DUT, for=20 instance, calibrate the cable together with an identical SMA connector and=20 coaxial probe? Celine >From: dgun@xxxxxxxxxx >Reply-To: dgun@xxxxxxxxxx >To: si-list@xxxxxxxxxxxxx >Subject: [SI-LIST] Re: S-parameter passivity... Interpreting the results. >Date: Sat, 24 Jun 2006 17:10:51 -0800 > >My understanding is that you are calibrating to the 3.5mm connector using=20 >t=3D >he >85052D cal kit, then trying to measure something at the end of an adapter=20 >a=3D >nd >length of cable. If this is the case, then I'm not surprised you see some >ripple (or "noise"). The ripple is likely due to the adapter and length of >cable. You would need to deembed this using a model of the probe or some=20 >so=3D >rt >of deembedding algorithm using reflects at the end of the probe. > >At a minimum, the electrical delay from the calibration plane to the end of >the probe should be calculated or measured and removed from the=20 >measurement. > >-- >Daniel > > > ----- Original Message ----- > > From: "travis ellis" <travissellis@xxxxxxxxx> > > To: "Hill, John" <jhill@xxxxxxxxxx>, si-list@xxxxxxxxxxxxx > > Subject: [SI-LIST] Re: S-parameter passivity... Interpreting the=20 >results. > > Date: Tue, 13 Jun 2006 09:19:29 -0700 (PDT) > >=3D20 > >=3D20 > > I'm using the 8052D broadband economy calibration kit. I've performed a =20 >=3D >full 2port SOLT=3D20 > > calibration calibrating out the cabling. All of which use 3.5mm=20 >connecto=3D >rs. Then I attach port=3D20 > > 2 to a 3.5mm - GPPO connector that attaches to a 0.085 gppo terminated=20 >c=3D >able on one end. The=3D20 > > other end of the cable (DUT) has a coaxial probe. Port 1 is attached to=20 >=3D >an sma to gpo=3D20 > > connector that is mounted in a brass block and ground smooth. This=20 >provi=3D >des a coaxial structure=3D20 > > that I make contact to with the coaxial probe that is on the other end=20 >o=3D >f the dut. > >=3D20 > > Travis > > "Hill, John" <jhill@xxxxxxxxxx> wrote: Travis, > >=3D20 > > Which Calibration kit are you using and can you describe what is between > > the calibration plane and the thing you are trying to model? BTW, what > > RF connector are you using? > >=3D20 > > Best regards, > >=3D20 > > John > >=3D20 > >=3D20 > >=3D20 > >=3D20 > > --------------------------------------- > > The information in this email and attachments hereto may contain=20 >legally=3D > privileged,=3D20 > > proprietary or confidential information that is intended for a=20 >particula=3D >r recipient. If you are=3D20 > > not the intended recipient(s), or the employee or agent responsible for=20 >=3D >delivery of this=3D20 > > message to the intended recipient(s), you are hereby notified that any=20 >d=3D >isclosure, copying,=3D20 > > distribution, retention or use of the contents of this e-mail =20 >informatio=3D >n is prohibited and may=3D20 > > be unlawful. When addressed to Takata customers or vendors, any=20 >informat=3D >ion contained in this=3D20 > > e-mail is subject to the terms and conditions in the governing=20 >contract,=3D > if applicable. If you=3D20 > > have received this communication in error, please immediately notify us=20 >=3D >by return e-mail,=3D20 > > permanently delete any electronic copies of this communication and=20 >destr=3D >oy any paper copies. > > --------------------------------------- > > -----Original Message----- > >=3D20 > > From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] > > On Behalf Of travis ellis > > Sent: Tuesday, June 13, 2006 11:00 AM > > To: si-list@xxxxxxxxxxxxx > > Subject: [SI-LIST] S-parameter passivity... Interpreting the results. > >=3D20 > > I've been taking measurements with a VNA then running them through a > > passivity checker. The basis for the code was originally posted by Ray. > > I've modified it to meet my needs. Added plotting capabilities, log mag > > format handling, and nudging of the non-passive values when only a few > > points are out of spec etc. I don't think I broke anything in the > > process but what I've noticed is that the eigen values of some of my > > measurements are very noisy. The better measurements oscillate too but > > they trend upward with increasing frequency. The suspect measurements > > oscillate between near 0 and approximately 0.4 from point to point > > across the higher frequency bands. The magnitude of the s-parameters > > seem to be noisy as well. I've gone through my setup to make sure that > > my cables don't have loose/bad connections. Replaced some connectors > > that seemed inadequate and while things got marginally better the > > measurements still contained noise. The noise source seems to be my > > fixturing. Unfortunately I don't think I can improve this given my >time > > constraints. > >=3D20 > > The only thing that I've noticed is that the time domain=20 >simulations > > take longer than those created with a data set that isn't as noisy. > >=3D20 > >=3D20 > > Is there a way to decide if these models are accurate enough to be > > reliable? > >=3D20 > > Regards, > >=3D20 > > Travis > > >--=3D20 >___________________________________________________ >Play 100s of games for FREE! http://games.mail.com/ > >------------------------------------------------------------------ >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: >http://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: > http://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: http://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: =20 http://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 =20 ------------------------------------------------------------------ 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: http://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: http://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