I have a question about extracting an accurate model from TDR IConnect. The question is that when I want to extract a DUT which the Impedance is not 50 ohm, (for example, an USB connector which the differential impedance is 90 ohm). Should I need to make a fixture to transfer impedance from single end 50 ohm to differential 90 ohm, And then connect between TDR and DUT. The purpose is to eliminate the discontinuity that maybe affect the model accuracy we extract. Or can I directly use the 50 ohm SMA cable connect the DUT to extract the model? The accuracy will be the same or not? I am worried because the USB connector is very short. If I directly use 50 ohm SMA cable, I am afraid that the discontinuity will cover all the model effect. Please give me some suggestions. Thanks for help, I am truly appreciated. David ------------------------------------------------------------------ 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 technical documents are available at: http://www.si-list.net 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