Scott, In your two cases below, I have the impression you are assuming that the person testing the s parameters has no knowledge of the construction of the object being represented by the s parameters. In that generality, you are quite correct. However, as I read the original question, the case where the tester has knowledge of the device under test and perhaps enven designed a test structure is not eliminated. Would you like commment on the specific case where one has a a set of data from a known test structure? Aubrey Sparkman 512-461-6165 asparky@xxxxxxxxxxxxxxxxxxxxxxxx -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Scott McMorrow Sent: Saturday, August 21, 2010 6:20 PM To: Luciano Boglione Cc: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: Causality test In general, no. Take the following 2 cases. Hypothetical material with zero loss and Er = 1 Case 1 - A single-ended trace that is 10 inch long in this material Case 2 - A single-ended trace that is folded back and forth in a 1 inch distance with a total length of 10 inchs In both cases the S2p file describes a trace that is X mm long. In case 1 a signal traveling from Port 1 to Port 2 will travel at the speed of light and arrive at port 2 approximately 847.25 ps after being launched from Port 1. In case 2 a signal traveling from Port 1 to Port 2 will travel at the speed of light, but will arrive at port 2 sooner than 847.25 ps after being launched, because some of the signal is coupled across the folded section and will begin arriving 84.725 ps after the launch at Port 1. Both systems are causal. Measurements of s-parameters of these cases would be causal, yet one will show the far end signal beginning to transition much earlier than the other. How could this be discerned by a test? regards Scott Scott McMorrow Teraspeed Consulting Group LLC 121 North River Drive Narragansett, RI 02882 (401) 284-1827 Business (401) 284-1840 Fax http://www.teraspeed.com TeraspeedR is the registered service mark of Teraspeed Consulting Group LLC On 8/21/2010 7:05 PM, Luciano Boglione wrote: > Hi folks, > > Is there a "test" that can be executed directly on a given S parameter set that can confirm causality of the network? Put yourself in the best possible conditions (e.g. off the top of my head, frequency ranges from DC to infinity continuously). I'm asking for something similar to a passivity test in the frequency domain. > > Thanks, > Luciano > > > > > > > . > > > Sent via BlackBerry from T-Mobile > ------------------------------------------------------------------ > 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 > > 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 technical documents are available at: http://www.si-list.net 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 technical documents are available at: http://www.si-list.net 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