[SI-LIST] Re: Differential S-parameters
- From: Steve Corey <steve@xxxxxxxxxxxxxx>
- To: "SI List (E-mail)" <si-list@xxxxxxxxxxxxx>
- Date: Fri, 11 Jan 2002 14:47:39 -0800
Mick -- one major issue here is that of linearity. In his original
post, Pat was asking about being able to measure nonlinear systems. If
the system is linear, then you can use superposition to add, subtract,
and scale the elements of the S matrix to get the different modal
responses. If it's nonlinear, you can't count on superposition, and you
will incur system-specific error.
-- Steve
-------------------------------------------
Steven D. Corey, Ph.D.
Time Domain Analysis Systems, Inc.
"The Interconnect Modeling Company."
http://www.tdasystems.com
email: steve@xxxxxxxxxxxxxx
phone: (503) 246-2272
fax: (503) 246-2282
-------------------------------------------
Zhou, Xingling (Mick) wrote:
>
> However, according to microwave network theory, S matrix is a 'complete'
> description of the port properties of the network in certain environment
> (reference impedances). To me, all port information is included, including
> diffrential and common or any other possible decompositions. In principle,
> differential signals are just special forms (or subset). Logically, the
> conversion should make sense. I am confused by "true". Is there any
> different differential thing?
>
> I agree that direct measurement is still an issue.
>
> Another question, is "single-ended" an officical term (in any formal
> publications)? It is the standard scattering parameters.
>
> Have a great weekend.
>
> Mick
>
> -----Original Message-----
> From: Dima Smolyansky [mailto:Dima@xxxxxxxxxxxxxx]
> Sent: Friday, January 11, 2002 1:46 PM
> To: mmunroe@xxxxxxxxxxxxxx; SI List (E-mail)
> Subject: [SI-LIST] Re: Differential S-parameters
>
>
>
> Hello,
>
> I think one important part that this author is missing is that Pat Zabinski
> was asking for "true" differential S-parameters measurement, not conversion
> of single-ended measurements into differential. Henri Merkelo's software
> would not be accurate as "true" differential S-parameter computation, since
> it is based on not true differential initial data, but conversion of
> single-ended into differential. Also, since Patrick seem to be interested in
> non-linear active (active is the key word) device characterization, in this
> case getting S-parameters from TDR does not seem to be the best thing, as
> TDR has not been widely used for active device characterization. We come
> across these questions about TDR all the time, and people believe it may be
> possible to do active device characterization with a DC blocking capacitor,
> but nobody seems to have done it.
>
> Another important (although non-technical) point that the author is missing
> is that it is inappropriate to mislead this newsgroup. None of DesignCon
> forums or papers is sponsored by anybody - at least not any more than any
> technical paper at a technical conference can be - they can only be
> co-authored. I know this because we have a TecForum and a paper at DesignCon
> ourselves (and our paper and TecForum will deal with exactly some of the
> technical issues analyzed above). Furthermore, ERNI is nowhere on
> DesignCon co-sponsor and nobody from ERNI is on a co-author list, to the
> best of my knowledge. I hope Mr. Monroe just mis-spoke accidentally.
>
> Thanks,
>
> ===================
> Dima Smolyansky
> Time Domain Analysis Systems, Inc.
> 11140 SW Barbur Blvd., Suite 100
> Portland, OR 97219
> (503) 246-2272
> (503) 246-2282 (fax)
> (503) 804-7171 (mobile)
>
> Download new IConnect(R) TDR software demo at www.tdasystems.com/download!
>
>
>
> ----- Original Message -----
> From: "mmunroe" <mmunroe@xxxxxxxxxxxxxx>
> To: <databits@xxxxxxxxxxxxx>
> Cc: "[unknown]" <si-list@xxxxxxxxxxxxx>
> Sent: Thursday, January 10, 2002 10:09 PM
> Subject: [SI-LIST] Re: Differential S-parameters
>
>
>
>>Gus,
>>
>>You might be interested in attending Dr. Merkelo's TechForum (sponsored b=
>>y
>>Agilent and ERNI) on Monday January 28th 9:00-12:00 as part of DesignCon.=
>>
>>
>>His Oculus-Cascade s-parameter acquisition method generates S21 and eye
>>patterns
>>using TDT methods and a mainframe differential TDR. Conversion between
>>2 and 4 port measurments, filtering, stubs and all sort of bit patterns a=
>>re
>>all part of the
>>work bench. He will be talking about the characterization of differentia=
>>l
>>components including
>>traces, stubs, connectors, etc... You can look at his paper from last
>>year's DesignCon.
>>
>>I will be glad to buy the first round of beer in the lobby bar following
>>the afternoon Tech Forum
>>on Monday. I will bring Oculus on my laptop if you want to look at some=
>>
>>collected files. Let me
>>know and I will be glad to send you some recent presentation pages.
>>
>>michael munroe
>>The ERNI Group
>>
>>
>>Message text written by INTERNET:databits@xxxxxxxxxxxxx
>>
>>>Getting a bunch of single-ended s-parameter that have been to differenti=
>>>
>>al
>>s-parameters is a neat mathematical system that allows _close_ correlatio=
>>n
>>to _simulators_ (like ADS, Serenade, others?) when the "ports" component =
>>is
>>used.
>>
>>In the simplest (most common) common simulation configurations, and using=
>> 4
>>ports, both of these systems use a perfect ground (i.e. node 0 reference)=
>>
>>on
>>both sides (i.e. at each port) of the device being measured. "Accurate"=
>>
>>can be a word used to describe this comparison.
>>
>>I can not say that "accurate" is incorrect. Measuring what is being
>>modeled
>>and vice versa is a good thing.... however, for the measurements or the
>>model have anything to do with system performance, the currents should
>>return through the same path as is in the real system.
>>
>>
>>I have been trying to understand a better way of creating a differential
>>s-parameter measurement/simulation that is more indicative of SYSTEM
>>performance. What I am struggling with is the same things as stated by
>>Mick, Patrick and Chuck.
>>
>>
>>Random Thought from the empirical perspective....
>>I like the baluns concept.... but these usually only have a very limited
>>bandwidth. A different way (notice I did not say better) to approach the=
>>
>>problem may be to only measure differential "s11". Basically, connect
>>port1 from 2 VNAs to two terminals on one side of the DUT (shifting the
>>phase of one of the VNAs 180, I wonder what the best way is to do that?).=
>>
>>Then terminating the far end TO THE RETURN PATH through the device (yes, =
>>we
>>will have to have a "known termination")... look at the return loss for
>>each
>>port.... then some math to get the results, The test may then need to g=
>>et
>>repeated with the DUT flipped ( s22'ish )... and on and on and on and
>>on.... Yuck... I will break the equipment budget with this one. :)
>>
>> |-------|
>> | P1|---------|
>> |VNA1 | |
>> | P2| |
>> |-------| | |-----|
>> | -----> | | ---/
>> | DUT | \ Far End
>> |-------| | -----> | | ---/
>> | P1|---------| (inv) |-----|
>> |VNA2 |
>> | P2|
>> |-------|
>>In this diagram at least all the currents will return through the device
>>back to the source through a return path similar to that of the
>>application.
>>
>>
>>
>>
>>Boy this sure would be messy... There is probably a better way to do this=
>>
>>in
>>simulation... How about using multiport single ended measurements to ful=
>>ly
>>"port-wise" characterize" devices... confirm these results to a model....=
>>
>>Then take advantage of the simulator, install an empirically confirmed
>>models... Is it possible to create non-ground referenced (i.e. amplifier =
>>to
>>be referenced to a lossy return path) differential amplifier models?
>>
>>Depending on how they work, those "no-ground" ports could come in handy
>>here!
>>
>>Too many random thoughts.... [richochet_rabbit_mode=3Doff]
>>
>>_gus
>>
>>How many of you will be at DesignConn??? How about a pizza, beer, and
>>differential s-parameters evening (or two) to set up a plan to figure thi=
>>s
>>out?
>>
>>
>>-----Original Message-----
>>From: si-list-bounce@xxxxxxxxxxxxx
>>[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Gary Otonari
>>Sent: Thursday, January 10, 2002 4:15 PM
>>To: xlzhou@xxxxxxxxx; si-list@xxxxxxxxxxxxx
>>Subject: [SI-LIST] Re: Differential S-parameters
>>
>>
>>
>>There is no "true" differential VNA that we know of today, but at GigaTes=
>>t,
>>we have been using the Agilent Multiport for Mixed-mode (common and
>>differential) S-parameter measurements, with good results. We have don=
>>e
>>several correlation experiments to verify that direct TDR measurements
>>agree with the differential S-parameters (via simulation in ADS). For a
>>clear, well written App. Note on the subject of single-ended and
>>differential S-parameters, which references the Blockelman paper, see
>>Maxim's App Note #HFAN-510:
>>
>>http://pdfserv.maxim-ic.com/arpdf/AppNotes/4hfan510.pdf
>>
>>We'll be discussing differential measurements, including the Agilent 4-po=
>>rt
>>VNA, several times in public during the month of January. I'll send a
>>separate note to the list, with our upcoming schedule of events....
>>
>>-- Gary
>>
>>=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
>>
>>"Zhou, Xingling (Mick)" wrote:
>>
>>
>>>Dennis,
>>>
>>>Sorry for the errors. It should be
>>>
>>>MTT-Vol.45,No.7,1997,pp.1071-1077.
>>>
>>>The title is "Pure-Mode Network Analyzer for On-Wafer Measurements of
>>>Mixed-Mode S-Parameters of Differential Circuits" by David E. Blockelma=
>>>
>>n
>>
>>>etc.
>>>
>>>Thanks for pointing it out.
>>>
>>>Mick
>>>
>>>-----Original Message-----
>>>From: Dennis Rehm [mailto:drehm@xxxxxxxx]
>>>Sent: Thursday, January 10, 2002 2:32 PM
>>>To: xlzhou@xxxxxxxxx
>>>Subject: Re: [SI-LIST] Re: Differential S-parameters
>>>
>>>I looked on the MTT web site and did not find the article that you
>>>mentioned below. The pages in No. 1 start at 1, the july issue has page=
>>>
>>s
>>
>>>in the 1000 to 1100 range but no article starting on page 1071. What i=
>>>
>>s
>>
>>>the title of the paper?
>>>
>>>Thanks
>>>
>>>Dennis
>>>
>>>"Zhou, Xingling (Mick)" wrote:
>>>
>>>
>>>>Hi,
>>>>
>>>>We have exactly the same concern.
>>>>
>>>>I use the formulas published in MTT-Vol47,No.1,1999,pp.1071-1077. The=
>>>>
>>>>authors proposed PMVNA system. I do not know any commericial one.
>>>>
>>>>Furthermore, how does the "Network Analyzer with Ungrounded Ports
>>>>(SP_Diff.)" in Agilent ADS
>>>>work in this case? I mean, are the definitions consistent?
>>>>
>>>>Mick
>>>>
>>>>-----Original Message-----
>>>>From: Zabinski, Patrick J. [mailto:zabinski.patrick@xxxxxxxx]
>>>>Sent: Thursday, January 10, 2002 9:23 AM
>>>>To: si-list@xxxxxxxxxxxxx
>>>>Subject: [SI-LIST] Differential S-parameters
>>>>
>>>>In the past few years, we've seen a tremendous surge
>>>>in the application of differential signaling, and we
>>>>do not expect the trend to end anytime soon.
>>>>
>>>>In our lab, we like to characterize our devices, both
>>>>active and passive, with S-parameters. We feel S-parameters
>>>>give us MUCH useful information.
>>>>
>>>>However, making differential S-parameter measurements
>>>>takes us a considerable amount of effort, requiring
>>>>a series of baluns, switches, etc., all manually
>>>>controlled/installed.
>>>>
>>>>Is there a commercial piece of equipment on the market
>>>>(or being developed) that makes truly differential S-parameters.
>>>>
>>>>I am aware of the ATN/Agilent system that takes single-ended
>>>>measurements and mathematically converts the results to
>>>>differential, but for active/non-linear devices, I believe
>>>>we really need a truly-differential capability. Does such
>>>>a beast exist?
>>>>
>>>>Thanks,
>>>>Pat
>>>>
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>>From: "databits" <databits@xxxxxxxxxxxxx>
>>To: <si-list@xxxxxxxxxxxxx>
>>Subject: [SI-LIST] Re: Differential S-parameters
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