Dima, "a priori" That's exactly my point. If you don't already know the answer, you can't determine the exact topology with either instrument. Not that it really matters; the circuit connected to the ports won't care whether you have the exact topology or an equivalent topology.=20 Aubrey Sparkman=20 Enterprise Engineering Signal Integrity Team Dell, Inc.=20 Aubrey_Sparkman@xxxxxxxx=20 (512) 723-3592 "The ultimate measure of a man is not where he stands in moments of comfort and convenience, but where he stands at times of challenge and controversy." - Martin Luther King, Jr. -----Original Message----- From: dmitry.a.smolyansky@xxxxxxxxxxxxxx [mailto:dmitry.a.smolyansky@xxxxxxxxxxxxxx]=20 Sent: Thursday, August 30, 2007 5:52 PM To: Sparkman, Aubrey; zhenggang.cheng@xxxxxxxxx; si-list@xxxxxxxxxxxxx Subject: RE: [SI-LIST] Re: TDR S-parameter and correlation Aubrey, I would think the answer is unambiguous yes, if you do not have splits and stubs. And you do have splits and stubs, the answer is also yes, but qualified with "if you know enough about your topology a priori." Thanks, =20 Dima Smolyansky Tektronix, Inc. P.O. Box 500, MS 39-111 Beaverton, OR 97077-0001 503-627-7180 503-627-2260 (fax) -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Aubrey_Sparkman@xxxxxxxx Sent: Thursday, August 30, 2007 1:06 PM To: zhenggang.cheng@xxxxxxxxx; si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: TDR S-parameter and correlation Here's a thought: Even if you use a TDR, do you really think you can tell exactly what the topology is, if it's in a box and you can't see it?=3D20 Aubrey Sparkman=3D20 Enterprise Engineering Signal Integrity Team Dell, Inc.=3D20 Aubrey_Sparkman@xxxxxxxx=3D20 (512) 723-3592 "The ultimate measure of a man is not where he stands in moments of comfort and convenience, but where he stands at times of challenge and controversy." - Martin Luther King, Jr. -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of ZHENGGANG CHENG Sent: Thursday, August 30, 2007 2:30 PM To: si-list Subject: [SI-LIST] TDR S-parameter and correlation Hi, My question is: If we TDR (assuming the TDR method is 100% correct) the equivalent circuit converted using S-parameter, will the result is exactly the same as real TDR of the same DUT? (assume the converting error and bandwidth are not issues) Assume this DUT has many large discontinuities inside. To me, the real TDR can distinguish all the discontinuities inside a DUT; however, the S-parameter is only the characterization at the ports rather than inside. Will two equivalent circuits give the same S-parameter but have two different topologies? Look froward to your replies. Thanks, ZG ------------------------------------------------------------------ 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: =3D20 //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 =3D20 ------------------------------------------------------------------ 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: =20 //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: //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