[SI-LIST] Re: TDR Analsis Equipment..Tektronix vs Agilent?
- From: "Cavanna, Vicente Vaca (Sr. ; ProCurve ASICs)" <vicente.cavanna@xxxxxx>
- To: <tom@xxxxxxxxxxxxx>, <homer.si.mpson66@xxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Wed, 25 Apr 2007 19:18:37 -0000
Hi Tom,
I disagree that you need to get equal energy to the DUT. As Dima
observed, calibration takes care of non-uniformity of energy.=20
In other words, to characterize an unknown linear network from its
response to a particular stimulus you simply need to know the stimulus
and the response. It does not matter what the stimulus is. In practice
it does matter somewhat, since there is always noise to contend with. As
long as you can measure the stimulus and the response, either because
the stimulus is much larger than the noise, or because you use averaging
to cancel the noise, you can compute the network response.
The ability to resolve fine grained features in the time domain response
depends on the bandwidth over which you have stimulated the DUT rather
than the instrument you use (TDR or VNA). You can approximate the
bandwidth of the TDR by 0.5/tr where tr is the 10%-90% risetime of the
step (for steps that are gaussian in shape). However you also need to
know that there is sufficient energy at each frequency of interest.
I do agree that a DUT that that has the response that you originally
indicated (a resonance at some frequency) will present a greater
challenge (to both a VNA and a TDR) at that frequency but only because
of the ability to extract the response from the noise.
Vicente
> -----Original Message-----
> From: Tom Dagostino [mailto:tom@xxxxxxxxxxxxx]=20
> Sent: Wednesday, April 25, 2007 10:26 AM
> To: Cavanna, Vicente Vaca (Sr. ; ProCurve ASICs);=20
> homer.si.mpson66@xxxxxxxxx; si-list@xxxxxxxxxxxxx
> Subject: RE: [SI-LIST] Re: TDR Analsis Equipment..Tektronix=20
> vs Agilent?
>=20
> Vicente
>=20
> For the VNA case I was referring to I think you need to get=20
> equal energy to the point of interest or you will start=20
> losing resolution. With the TDR method you can see great=20
> resolution near the stimulus end but as the length
> (loss) of the system accumulates the resolution degrades, it=20
> is harder and harder to discern two different closely spaced=20
> discontinuities until they are blurred into one. Internally=20
> the TDR analysis engine knows the frequency response of the=20
> reference impulse and compares this to the reflected signal.
>=20
>=20
> This same effect will happen in the VNA's case I believe. As=20
> the bandwidth decrease at the feature of interest the ability=20
> to resolve two different closely spaced features will diminish.
>=20
> Regards,=20
>=20
> Tom Dagostino
> Teraspeed(R) Labs
> 13610 SW Harness Lane
> Beaverton, OR 97008
> 503-430-1065
> tom@xxxxxxxxxxxxx
> www.teraspeed.com=20
>=20
> Teraspeed Consulting Group LLC
> 121 North River Drive
> Narragansett, RI 02882
> 401-284-1827
>=20
> -----Original Message-----
> From: Cavanna, Vicente Vaca (Sr. ; ProCurve ASICs)=20
> [mailto:vicente.cavanna@xxxxxx]
> Sent: Wednesday, April 25, 2007 9:38 AM
> To: tom@xxxxxxxxxxxxx; homer.si.mpson66@xxxxxxxxx;=20
> si-list@xxxxxxxxxxxxx
> Subject: RE: [SI-LIST] Re: TDR Analsis Equipment..Tektronix=20
> vs Agilent?
>=20
>=20
> Hi Tom,
> But it is not too important to get the same energy over the=20
> measurement
> frequency range (after all, the energy in the TDR stimulus is=20
> hardly uniform
> over frequency). What is of primary importance is to have
> *sufficient* energy at the detector to overcome the noise=20
> (i.e. sufficient
> signal to noise ratio) at all frequencies of interest. I do=20
> agree of course
> that the DUT plays a huge part in how much energy reaches=20
> the detector.
> Vicente
>=20
> > -----Original Message-----
> > From: si-list-bounce@xxxxxxxxxxxxx
> > [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Tom Dagostino
> > Sent: Tuesday, April 24, 2007 6:32 PM
> > To: Cavanna, Vicente Vaca (Sr. ; ProCurve ASICs);=20
> > homer.si.mpson66@xxxxxxxxx; si-list@xxxxxxxxxxxxx
> > Subject: [SI-LIST] Re: TDR Analsis Equipment..Tektronix vs Agilent?
> >=20
> > Vicente
> >=20
> > It is not a problem getting a large amount of energy to the
> > DUT, it is a problem of getting the same energy over the=20
> > measurement frequency range. =3D If there is an inductive=20
> > launch it will act as a low pass filter. Thus the energy=20
> > will be different at different frequencies.
> >=20
> > Tom Dagostino
> > Teraspeed(R) Labs
> > 13610 SW Harness Lane
> > Beaverton, OR 97008
> > 503-430-1065
> > tom@xxxxxxxxxxxxx=3D20
> > www.teraspeed.com=3D20
> >=20
> > Teraspeed Consulting Group LLC
> > 121 North River Drive
> > Narragansett, RI 02882
> > 401-284-1827
> >=20
> > -----Original Message-----
> > From: si-list-bounce@xxxxxxxxxxxxx
> > [mailto:si-list-bounce@xxxxxxxxxxxxx] =3D On Behalf Of Cavanna,=20
> > Vicente Vaca (Sr. ; ProCurve ASICs)
> > Sent: Tuesday, April 24, 2007 5:20 PM
> > To: homer.si.mpson66@xxxxxxxxx; si-list@xxxxxxxxxxxxx
> > Subject: [SI-LIST] Re: TDR Analsis Equipment..Tektronix vs Agilent?
> >=20
> >=20
> > With a VNA one can increase the power level of the stimulus
> > and get =3D more energy into and through the DUT even when the=20
> > DUT is lossy and/or =3D extremely reflective. With a TDR this=20
> > is not as easy to do; in fact the TDRs I =3D have used do not=20
> > permit such control. Vicente
> >=20
> > > -----Original Message-----
> > > From: si-list-bounce@xxxxxxxxxxxxx=3D3D20 =3D20
> > >[mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Peter J
> > > Sent: Tuesday, April 24, 2007 9:36 AM
> > > To: si-list@xxxxxxxxxxxxx
> > > Subject: [SI-LIST] Re: TDR Analsis Equipment..Tektronix vs=20
> > Agilent?=3D20
> > >=3D3D20 Hi, The biggest problem in using a TDR or VNA for
> > that matter
> > >is=3D3D20 to get enough energy into the DUT since even a very
> > small=3D3D20
> > >inductance at the connection point from the TDR to the
> > DUT=3D3D20 will
> > >give an insertion loss. It's possible to get a return=3D3D20 loss =
of
> > >-20dB at 5GHz if you work hard. At 50 GHz it's hard=3D3D20 to=20
> > get -3 dB
> > >RL which means that half of the power will enter=3D3D20 the
> > DUT and the
> > >rest is wasted. By using a VNA it is possible=3D3D20 to make a TRL
> > >calibration kit and remove the effect of the=3D3D20 =20
> > testsystem and only
> > >get the DUT characteristics.
> > > I use a short pigtail with a thin semirigid coax instead of =
a=3D3D20
> > >probe when I do measurements with the TDR(tektronix). It=3D3D20 =20
> > >increases the accuracy a great deal.
> > >=3D3D20
> > > BR
> > > Peter
> > >=3D3D20
> > > -----Original Message-----
> > >=3D3D20
> > > From: si-list-bounce@xxxxxxxxxxxxx
> > >=20
> >=20
> [*mailto:si-list-bounce@xxxxxxxxxxxxx*<si-list-bounce@xxxxxxxxxxxxx>]
> > > On Behalf Of ext Asbenson, Lyndell L
> > >=3D3D20
> > > Sent: 24. april 2007 02:27
> > >=3D3D20
> > > To: heidi.barnes@xxxxxxxxxx; si-list@xxxxxxxxxxxxx =3D3D20
> > > Cc: timothy.j.nash@xxxxxxxx; tom_cip_11551@xxxxxxxxx =3D3D20
> > > Subject: [SI-LIST] Re: TDR Analsis Equipment..Tektronix=20
> vs Agilent?=20
> > >=3D3D20 Dedicated TDR is much easer to setup then going the VNA
> > route -Lyndell
> > >=3D3D20 -----Original Message----- =3D3D20
> > > From: si-list-bounce@xxxxxxxxxxxxx =20
> >=20
> >[*mailto:si-list-bounce@xxxxxxxxxxxxx*<si-list-bounce@xxxxxxxxxxxxx>
> > > ]
> > >=3D3D20
> > > On Behalf Of Barnes, Heidi
> > >=3D3D20
> > > Sent: Monday, April 23, 2007 12:17 PM
> > >=3D3D20
> > > To: si-list@xxxxxxxxxxxxx
> > >=3D3D20
> > > Cc: timothy.j.nash@xxxxxxxx; tom_cip_11551@xxxxxxxxx =3D3D20
> > > Subject: [SI-LIST] Re: TDR Analsis Equipment..Tektronix=20
> vs Agilent?=20
> > >=3D3D20 Hi Tom,
> > >=3D3D20
> > > Tim is correct in that probing is not a simple task. If=20
> > you=3D3D20 have
> > >the time and patience, a Vector Network Analyzer with=3D3D20 PCB
> > >Thru-Reflect-Line Calibration standards can provide a=3D3D20 =20
> > method for
> > >getting measured electrical data for a PCB=3D3D20 structure=20
> that does
> > >not include the probes or connectorized=3D3D20 transitions=20
> on to the=20
> > >printed circuit board. The S-Parameter=3D3D20 data can then=20
> > be converted
> > >to time domain for TDR analysis of=3D3D20 the discontinuities and =
a
> > >40GHz box will give you around an=3D3D20 18pS rise time pulse=20
> > (an edge
> > >that is ~100mils long for a PCB=3D3D20 dielectric constant of
> > ~4) which
> > >gives a significant amount=3D3D20 of detail (50mils is rather
> > ambitious
> > >unless you have money=3D3D20 for the top end 110GHz VNA's=20
> or 8pS rise
> > >time TDR scopes).=3D3D20 The other thing to think about is=20
> that most=20
> > >applications=3D3D20 running about 3Gbps are differential so=20
> > it is also
> > >nice to=3D3D20 have a 4-Port system for measurements.
> > >=3D3D20
> > > Regards,
> > >=3D3D20
> > > Heidi
> > >=3D3D20
> > > -----Original Message-----
> > >=3D3D20
> > > From: si-list-bounce@xxxxxxxxxxxxx =20
> >=20
> >[*mailto:si-list-bounce@xxxxxxxxxxxxx*<si-list-bounce@xxxxxxxxxxxxx>
> > > ]
> > >=3D3D20
> > > On Behalf Of Nash, Timothy J
> > >=3D3D20
> > > Sent: Monday, April 23, 2007 11:33 AM
> > >=3D3D20
> > > To: tom_cip_11551@xxxxxxxxx; si-list@xxxxxxxxxxxxx =3D3D20
> > > Subject: [SI-LIST] Re: TDR Analsis Equipment..Tektronix=20
> vs Agilent?=20
> > >=3D3D20 Hi, Tom.
> > >=3D3D20
> > > I have tried using a Tektronix TDR (I'm not sure of the=3D3D20
> > > model) to probe PCBs before, and found that what probe=20
> > you=3D3D20 were
> > >using, and WHAT you were probing, can make or break your=3D3D20
> > >measurement. We were using a hand-held pressure-actuated=20
> type=3D3D20 =20
> > >probe and simply bending your wrist a little would change=20
> the=3D3D20 =20
> > >response. We had a tough time even discerning between=20
> two=3D3D20 vias=20
> > >spaced an inch apart from each other. I believe the=3D3D20 =20
> > probes used
> > >by most PCB manufacturers are on a robotic arm=3D3D20 and they are
> > >probing PCB coupons that have pre-defined TDR=3D3D20 =20
> > features. I found
> > >it very difficult to glean much useful info=3D3D20 from real
> > PCB traces
> > >when the discontinuities were as close=3D3D20 together as
> > what you are
> > >describing. I don't believe this was=3D3D20 a fault of the
> > scope - just
> > >a function of the probing method=3D3D20 and the feature
> > constraints of
> > >the PCB.
> > >=3D3D20
> > > Tim
> > >=3D3D20
> > >=3D3D20
> > >=3D3D20
> > >=3D3D20
> > >=3D3D20
> > > -----Original Message-----
> > >=3D3D20
> > > From: si-list-bounce@xxxxxxxxxxxxx =20
> >=20
> >[*mailto:si-list-bounce@xxxxxxxxxxxxx*<si-list-bounce@xxxxxxxxxxxxx>
> > > ]
> > >=3D3D20
> > > On Behalf Of tom_cip_11551
> > >=3D3D20
> > > Sent: Monday, April 23, 2007 10:47 AM
> > >=3D3D20
> > > To: si-list@xxxxxxxxxxxxx
> > >=3D3D20
> > > Subject: [SI-LIST] TDR Analsis Equipment..Tektronix vs Agilent?=20
> > >=3D3D20 Hi to the Signal Integrity community.
> > >=3D3D20
> > > I am looking for a set of equipment with wich to do=20
> > TDR=3D3D20 analysis
> > >on=3D3D3D3D20 high speed PCB structures. We are now=3D3D20
> > building boards
> > >to run at=3D3D3D3D20 speeds of 3 Gb/s or faster and=3D3D20 I
> > would like to
> > >resolve=3D3D3D3D20 discontinuites within, say, 50=3D3D20 mils
> > to 80 mils
> > >of each other.
> > >=3D3D20
> > > I have gotten quotes from Tektronix and Agilent for TDR=3D3D20
> > >equipment. =3D3D3D3D20 =3D3D20 The Tektronix system consists of =
the=20
> > >DSA8200 digital sampling=3D3D20 =3D3D3D scope,=3D3D3D3D20 the =
80E04 TDR=20
> > >sampling module and the =3D
> > 80SICON=3D3D20
> > > signal integrity and=3D3D3D3D20 failure analysis software (a
> > $20K=3D3D20
> > >item by itself).
> > >=3D3D20
> > > The Agilent system consists of the 86100C scope, the 54754A=3D3D20
> > >TDR=3D3D3D3D20 module and various other software programs=20
> for S=3D3D20 =20
> > >parameters, Jitter=3D3D3D3D20 analysis, etc.
> > >=3D3D20
> > > I am wondering what the Signal Integrity community at large=3D3D20 =
=20
> > >is=3D3D3D3D20 using.
> > > Which system is more popular and, most important,=20
> cost=3D3D3D3D20 =3D3D
> > effective?
> > >=3D3D20
> > > What are some of the advantages and drawbacks of each? =3D3D20
> > > Are there other solutions on the market that are more cost=20
> > >effective?=3D20 =3D3D20 Thank You =3D3D20 Tom =3D3D20 =3D3D20 =
=3D3D20
> > > ------------------------------------------------------------------
> > >=3D3D20
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