# Thread: SOLT cal short or open fringe parameters

Replies: 73 - Pages: 5 - Apr 24, 2012 12:43 PM Last Post By: Lucux Threads: [ | Next ]
 Posts: 2,793 Registered: 12/01/05
Re: SOLT cal short or open fringe parameters
Posted: Jun 11, 2011 9:45 AM   in response to: Lucux
 The apparent fringing capcitance will change. Since you have phase change linearly with frequency, I think that is why you have such a big C1 term. In my experience, the phase vs freq should have a very small shift, perhaps 5 degrees at 6 GHz. The capacitive polynomial doesn't account well for delay, and since you phase vs freq is nearly linear, it means you still have some effective delay in your result. As you point out, fringing capacitance cannot go negative (become inductive) so if you phase vs freq goes past 180 degrees, you MUST not be accounting properly for delay. Add delay until you phase vs freq is flat, and phase just does not quite go positive anywhere, then compute you capactive polynomieal.ripples on a long-line short (I recommended short, not open, as opens can have some radiation that confuses things), will give you a combination of goodness of c0 and load. If you have a bad load, it will set a baseline ripple, if you have a bac c0, it will add to the ripple.
 Posts: 54 Registered: 08/21/09
Re: SOLT cal short or open fringe parameters
Posted: Jun 21, 2011 6:58 AM   in response to: Lucux
 Dr. Joel,is there any reply? thanks.
 Posts: 54 Registered: 08/21/09
Re: SOLT cal short or open fringe parameters
Posted: Jun 21, 2011 7:02 AM   in response to: Lucux
 sorry, i did not notice there is page #2.
 Posts: 54 Registered: 08/21/09
Re: SOLT cal short or open fringe parameters
Posted: Jun 21, 2011 7:45 AM   in response to: Lucux
 20mm contact in air HFSS model.JPG (92.9 KB) 21mm is deembedded cx coefficient terms.JPG (122.9 KB) 21mm is deembedded fringe capacitance.JPG (104.4 KB)
 thanks Dr. Joeli'm still getting strange big c1 term. see attached please. see if you can advise to improve this situation? thanks again.
 Posts: 54 Registered: 08/21/09
Re: SOLT cal short or open fringe parameters
Posted: Jun 21, 2011 7:46 AM   in response to: Lucux
 21mm is deembedded phase shift less than 5 degrees.JPG (93.2 KB)
 Posts: 2,793 Registered: 12/01/05
Re: SOLT cal short or open fringe parameters
Posted: Jun 21, 2011 8:58 AM   in response to: Lucux
 I'll ask again: can you post your results as an S1P file for the S11 of the open standard. You don't need to add any delay, just post the results of your EM simulation.
 Posts: 54 Registered: 08/21/09
Re: SOLT cal short or open fringe parameters
Posted: Jun 21, 2011 7:27 PM   in response to: Lucux
 open without adding dely.s1p (79.2 KB)
 here is the s1p file.
 Posts: 2,793 Registered: 12/01/05
Re: SOLT cal short or open fringe parameters
Posted: Jun 22, 2011 12:52 AM   in response to: Lucux
 OpenWithDelay.png (38.7 KB) openwith141_334psdelay.s1p (21.8 KB)
 I find the delay to be about 144.334 psec (sorry, the offset delay is half this number, 72.167 ps), and the residual c0 term to be around 1.2 fF. Here are my results:And here is the S1P file if you want to compute the capacitance from the phase and align it with the polynomialopenwith141_334psdelay.s1p
 Posts: 2,793 Registered: 12/01/05
Re: SOLT cal short or open fringe parameters
Posted: Jun 22, 2011 1:00 AM   in response to: Lucux
 OpenWithDelay66_7.png (40.8 KB)
 And, if I use your expected delay of 66.7 ps (time 2 for elect delay function) I get almost exactly 80 fF across frequency, note the two marker values which display equivalent shunt capacitance
 Posts: 54 Registered: 08/21/09
Re: SOLT cal short or open fringe parameters
Posted: Jun 22, 2011 7:45 AM   in response to: Lucux
 thanks Dr. Joel,can you let me know how you generated these two plots? did you de embed the delay time? or did you use port extension or something similiar? how did you get the direct capacitance reading directly on the plot? did you input some equations?thanks again.
 Posts: 2,793 Registered: 12/01/05
Re: SOLT cal short or open fringe parameters
Posted: Jun 22, 2011 9:16 AM   in response to: Lucux
 very simply: I recalled the S1P file into the PNA. I put up a phase trace. I put up a marker and hit "marker:marker functions: marker>delay" then I moused over the marker and right click to get the Marker... dialog (also available under the soft keys Marker, Marker Properties) and I changed the marker default to be G+jB, which is the readout for the the inverse smith chart. And plotted the first plot. I then hit "save data as S1P" to save data.Then I set the delay (under scale:electrical delay) to be 66.7ps*2 (if I used port extension, it would automatically know it is a reflectiona and do the times 2 for me, but electrical delay doesn't do that), Put up a second marker, did the same thing. And plotted the second plot.
 Posts: 54 Registered: 08/21/09
Re: SOLT cal short or open fringe parameters
Posted: Jun 23, 2011 2:55 AM   in response to: Lucux
 PNA cannot recall snp file.JPG (45.1 KB)
 thanks Dr. Joeli read my PNA help file. it seems to me that it cannot recall SNP file. is there any other way to do this?
 Posts: 1,543 Registered: 11/16/05
Re: SOLT cal short or open fringe parameters
Posted: Jun 23, 2011 5:30 AM   in response to: Lucux
 You need to have at least firmware A.09.20 to have the .sNp file recall functionality.
 Posts: 54 Registered: 08/21/09
Re: SOLT cal short or open fringe parameters
Posted: Jun 24, 2011 12:19 AM   in response to: Lucux
 222.JPG (100.4 KB) 111.JPG (100.3 KB)
 thanks. i have upgraded the PNA firmware version to A.09.33.09. it can recall SNP now. see attached plots which looks very similiar to what Joel got. does this mean that i can get a few points at the curve and fit the polynomial and solve it to get coefficients of c0, c1, c2 and c3? thanks again.
 Posts: 2,793 Registered: 12/01/05
Re: SOLT cal short or open fringe parameters
Posted: Jun 24, 2011 12:30 AM   in response to: Lucux
 Well, it does mean it's possible, It's up to you to do the work, I suppose.