I find the Tek equipment much more intuitive than the Agilent. I usually can get what I need out of the Agilent, but it takes much longer. And, sometimes I haven't been able to get what I want, but I'll leave open the possibility I'm missing something that a more experienced user can find and/or my equipment is out of date. I know others have echoed my feelings; I look forward to seeing comments from folks who have had positive experiences w/ the Agilent and/or Sparq and have reasons for preferring them. I've witnessed it proven that the Tek can provide very accurate 2-port S-parameters using IConnect, see http://www.tek.com/products/oscilloscopes/sampling/interconnect_analysis/customer_papers/vna_tdr_correlation.pdf I expect these results could also be replicated on the Agilent and/or Sparq. Of course, there's going to be a difference in the dynamic range between the TDR and VNA, so don't expect to measure massively lossy systems with a TDR. The Tek provides differential excitation; the Agilent performs single-ended measurements and derives the differential response from those (Sparq too?). Theoretically nothing wrong with that - that's what VNA's do also. But, on the practical side, I've been able to use Tek's differential probes (P80318) to measure SDD21 of actual traces on product boards. This wouldn't be practical if I couldn't take advantage of the purely differential signaling to preclude the need for ground connections. Some caveats: * I measured extremely long traces to minimize the effect of launch discontinuities on the results * I used traces close to the top and backdrilled vias so their effects were minimal * I wouldn't want to quote my results very precisely, especially after about 10GHz * Don't try this with cruddy cables - the skew has to be in the sub picosecond range But, the measurements were enough to clearly discern the SDD21 difference between "bad" and "good" boards. The P80318 probes are also nice for quick differential impedance measurements since you don't need a ground connection; it would only work with the Tek. Also, you didn't mention how many ports you're hoping to measure, though you imply >2 since you're getting a separate sampler. As Cherry's paper (link above) demonstrates, TDR/TDT works just fine for 2-port measurements. If you're going above 2 ports, you have a completely different beast to wrestle: femtoseconds of skew will influence your measurements. For some limited cases or coarse measurements, I've been able to make the Tek work for >2 ports, but wouldn't want to push it too far. I haven't heard of a calibration scheme from Tek to accommodate this; I've crafted my own but it takes a lot of effort. Perhaps Agilent or Sparq do better here. 4-port VNAs have calibration algorithms to solve the problem. I think folks would find risetimes of about 15 ps out of both the Agilent and Tek; PicoSecond Pulse labs has modules if you need faster, and I think the Sparq is faster. Of course, this is purely opinion, and I'd probably be loyal to the Agilent or Sparq if I'd used them more. My $0.02... Jeff Loyer -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Dan Sent: Tuesday, November 02, 2010 3:15 PM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] TDR equipments -- comments or reviews Hi all, I am planning to buy TDR equipments. I have shortlisted two equipments, one from Agilent and anther Tektronix, along with the mainframe. Can anybody let me know your comments or reviews about these equipment and your advice or idea to buy this? I am also planning to do s-parameter extraction from the TDR measurement. So i need to TDT also. So i am adding a samping module. Agilent: mainframe: 86100C (option202 for extarcting s-parameter touchstone) TDR: 54754A (can anyone tell me the achievable rise time or frequency in this module) Sampling module: 86112A Tektronix: mainframe: DSA8200 (80SSPAR Iconnect for s-parameter extraction) TDR: 80E04 (can anyone tell me the achievable rise time or frequency in this module) Sampling module for TDT: 80E03 Is TEK better than Agilent. Is TEK's Iconnect outperforms Agilent's option 202 in the mainframe to extract s-parameter touchstone? Thank You for your time. DAN ------------------------------------------------------------------ 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