Take a look at this Oracle Design Con13 paper: 13-WP5 Impact of Probe Coupling on the Accuracy of Differential VNA Measurements It tries to quantify the amount of crosstalk caused by the PCB probes when making probe measurements. These effects can be calibrated when the isolation step of the calibration is performed, but this brings up even more problems. BR Gert ---------------------------------------- Absender ist HARTING Electronics GmbH, Marienwerderstraße 3, D-32339 Espelkamp; Registergericht: Amtsgericht Bad Oeynhausen; Register-Nr.: HRB 8808; Vertretungsberechtigte Geschäftsführer: Dipl.-Kfm. Edgar-Peter Düning, Dipl.-Ing. Torsten Ratzmann, Dipl.-Wirtschaftsing. Ralf Martin Klein -----Ursprüngliche Nachricht----- Von: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] Im Auftrag von Ippich, Alexander Gesendet: Montag, 27. Oktober 2014 07:39 An: arnshah@xxxxxxxxx Cc: si-list@xxxxxxxxxxxxx; Ippich, Alexander Betreff: [SI-LIST] AW: 40 GHz probe calibration Arnav, I can confirm, that when attempting to calibrate GSSG style microprobes with 1000um S/G pitch, I also do see return loss much worse than 20dB at 40GHz. The probes were calibrated with the recommended calibration substrate from the same supplier. The measurement protocol that was shipped with the probes states a S11 of around -5dB at 40dB into a 50ohm load. I would recommend using GSG style probes and smaller pitches to alleviate the issue. Best regards, alex -----Ursprüngliche Nachricht----- Von: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] Im Auftrag von Arnav Shah -X (arnshah - BBI TECHNOLOGIES INC at Cisco) Gesendet: Sunday, October 26, 2014 8:16 PM An: si-list@xxxxxxxxxxxxx Betreff: [SI-LIST] 40 GHz probe calibration Hello all, I am attempting a 40GHz calibration. I previously tried calibrating with 1000um pitch G S S G differential probes without success. I think at 40GHz there is no resonance, or planar waves on the cal substrate. Crosstalk is the main problem; I will try calibrating with <500um probes. Is there a way to measure/calculate this crosstalk? How can I verify this hypothesis? Right now, I define a good cal as return loss below 20dB, is there any other information I can use in determining a good cal? Thank you! -Arnav ------------------------------------------------------------------ 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 forum is accessible at: http://tech.groups.yahoo.com/group/si-list List archives are viewable at: //www.freelists.org/archives/si-list 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 forum is accessible at: http://tech.groups.yahoo.com/group/si-list List archives are viewable at: //www.freelists.org/archives/si-list 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 forum is accessible at: http://tech.groups.yahoo.com/group/si-list List archives are viewable at: //www.freelists.org/archives/si-list Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu