From: Bob Lewandowski ([email protected])
Date: Thu Oct 19 2000 - 19:03:31 PDT
I concur with all the semi-rigid coax comments. Most all of the commercial
probes I've seen generate large launch discontinuities (~20%), with the
exception of Picoprobe, and Cascade Microtech (both $$$ !).
I've used .047" diameter coax, either solid jacket or the tin dipped braid type
(very flexible). Tensolite/QMI sell .047 cable assemblies of the braid type
with male or female SMAs, that they call Semi-Flex. Just buy a 1 ft. cable and
chop it in half, match the lengths for differential. With the small coax you
can solder the jacket to a board ground next to a trace, and with a very short
center conductor, keep the launch reflection down to around 5%. Semi-rigid coax
typically can be obtained with tight tolerance on the Z0, so the cable becomes a
good reference impedance before the launch. Be cautious about minimizing the
length, as the small stuff is pretty lossy and degrades rise time.
---Bob Lewandowski
Vixel Corp.
Ken Taylor wrote:
> John Fisher's solution below is a very good one that I have used
> extensively. Although a little clumsy mechanically (you will want to use a
> probe positioner, hold the probe at about 45 degrees to get the tips and the
> ground to contact, keep the tips and ground path VERY short like 2 mm or so)
> they give great results. One more thing, however: If the probe impedance
> doesn't match your DUT impedance, you will get reflections etc. and you
> won't be able to see anything close in to the contact point. To solve that,
> match the impedances as closely as possible, keep the probe (semi rigid
> stuff) more than, say, 6" long, and then all the mismatch will be at the
> flexible cable/probe connection, and you can keep it out of the way of your
> measurements. These probes work well for 17 pS Tr.
> One last thing, these things were whipped up for customers by friendly Tek
> AEs, and weren't part numbered for sale. (How can you charge $5000 for these
> things? Can't, so they don't sell them!) The real Tek (and Agilent) probes
> looked nice, are definitely nicer mechanically, but can't hold a light to
> these "do it yourself" probes.
>
> Regards, Ken.
>
> Ken Taylor
> Polar Instruments, Portland, OR, USA.
> [email protected]
>
> John said
> <<We have built these using equal length sections of semi rigid coax with
> sma's at one end. The semi rigid copper outer shield is soldered together
> approx. every 3 ". Prepare the ends by careful cutting of the
> shield with an exacto knife, than solder the center conductors to
> the launch point vias or pads. Tektronix shipped some of these to
> us as accessories when we bought their IPA-510 a few years ago. I
> might be able to find a tek part number but someone like Micro-Coax could
> make some for you or find an off the shelf semi rigid assembly with sma's
> on both ends and then just cut it in half. Be carful not to bend it too
> much and kink it. These can also make nice 50 Ohm 10x passive
> probes with the addition of a series 450 resistor at the end.<br> >>
>
> ----- Original Message -----
> From: "si-list-digest" <[email protected]>
> To: <[email protected]>
> Sent: Thursday, October 19, 2000 5:00 PM
> Subject: si-list-digest V1 #286
>
> >
> > si-list-digest Thursday, October 19 2000 Volume 01 : Number
> 286
> >
> >
> >
> > In this issue:
> >
> > 1.) [SI-LIST] : High Frequency Seminar
> > "chasgra" <[email protected]>
> >
> > 2.) [SI-LIST] : SI - Salary Survey
> > sainath nimmagadda <[email protected]>
> >
> > 3.) [SI-LIST] : Differential TDR probes
> > "zanella, fabrizio" <[email protected]>
> >
> > 4.) Re: [SI-LIST] : Differential TDR probes
> > "Ritesh Kapahi" <[email protected]>
> >
> > 5.) Re: [SI-LIST] : Differential TDR probes
> > [email protected]
> >
> > 6.) RE: [SI-LIST] : Differential TDR probes
> > "Daniel, Erik S." <[email protected]>
> >
> > 7.) Re: [SI-LIST] : Differential TDR probes
> > John Fisher <[email protected]>
> >
> >
> > ----------------------------------------------------------------------
> >
> > Date: Wed, 18 Oct 2000 18:30:58 -0700
> > From: "chasgra" <[email protected]>
> > Subject: [SI-LIST] : High Frequency Seminar
> >
> > This is a multi-part message in MIME format.
> >
> > - ------=_NextPart_000_000C_01C03931.8EE7A3A0
> > Content-Type: text/plain;
> > charset="iso-8859-1"
> > Content-Transfer-Encoding: quoted-printable
> >
> > Rocky Mountain Chapter EMC Society presents:
> >
> > High Frequency Measurements and Noise in Electronic Circuits
> > - - one day demonstration based seminar.
> >
> > An informative and entertaining multimedia seminar for digital and =
> > analog designers as well as test engineering and EMC personnel.=20
> >
> > by Douglas C. Smith=20
> >
> > Author of High Frequency Measurements and Noise in Electronic Circuits=20
> >
> > An Unusual Seminar - Sign up here.
> >
> > This seminar is unique. Demonstrations on real circuits are used to =
> > illustrate most of the concepts being taught unlike most seminars which =
> > are taught through the use of vu-graphs as the main medium. About 70% of =
> > class time is spent in demonstrations. Complicated math is avoided. This =
> > format makes the seminar more interesting to the students and helps them =
> > to achieve a deeper understanding of the material covered. Many students =
> > have said that this was the best technical seminar they ever attended!=20
> >
> >
> >
> > When: Dec 1 2000
> >
> > If you are interested then goto our weblink: =
> > http://www.ewh.ieee.org/r5/denver/rockymountainemc
> >
> > Look for the Dec 1 meeting link and sign up!!
> >
> > Charles Grasso
> > Vice Chair RMCEMCS
> >
> >
> > - ------=_NextPart_000_000C_01C03931.8EE7A3A0
> > Content-Type: text/html;
> > charset="iso-8859-1"
> > Content-Transfer-Encoding: quoted-printable
> >
> > <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
> > <HTML><HEAD>
> > <META content=3D"text/html; charset=3Dwindows-1252" =
> > http-equiv=3DContent-Type>
> > <META content=3D"MSHTML 5.00.2919.6307" name=3DGENERATOR></HEAD>
> > <BODY bgColor=3D#ffffff>
> > <DIV><FONT size=3D2>
> > <P align=3Dcenter><A name=3DTitle><FONT size=3D6>Rocky Mountain Chapter =
> > EMC=20
> > Society</FONT></A><FONT size=3D6> presents:</FONT></P>
> > <P align=3Dcenter><FONT color=3D#0000ff face=3DArial size=3D6><B>High =
> > Frequency=20
> > Measurements and Noise</B></FONT> <FONT color=3D#0000ff face=3DArial =
> > size=3D6><B>in=20
> > Electronic Circuits<BR></B></FONT><FONT color=3D#0000ff face=3DArial =
> > size=3D5><B>- one=20
> > day demonstration based seminar.</B></FONT></P>
> > <P align=3Dcenter><FONT size=3D5><I>An informative and </I></FONT><FONT=20
> > color=3D#ff0000 size=3D5><B><I><U>entertaining</U></I></B></FONT><FONT =
> > size=3D5><I>=20
> > multimedia seminar for digital and analog designers as well as test =
> > engineering=20
> > and EMC personnel.</I></FONT> </P>
> > <P align=3Dcenter><FONT face=3DArial size=3D4><B>by </B></FONT><A=20
> > href=3D"http://www.ewh.ieee.org/r5/denver/rockymountainemc/1dayemc.htm#Ab=
> > out The Instructor"><FONT=20
> > face=3DArial size=3D4><B>Douglas C. Smith</B></FONT></A> </P>
> > <P align=3Dcenter><FONT size=3D4>Author of <I>High Frequency =
> > Measurements and Noise=20
> > in Electronic Circuits</I></FONT> </P>
> > <P align=3Dcenter><A=20
> > href=3D"http://www.ewh.ieee.org/r5/denver/rockymountainemc/seminarsignup.=
> > htm"><FONT=20
> > size=3D5><B><U>An Unusual Seminar - Sign up here.</U></B></FONT></A></P>
> > <P align=3Dleft>This seminar is unique. Demonstrations on real circuits =
> > are used=20
> > to illustrate most of the concepts being taught unlike most seminars =
> > which are=20
> > taught through the use of vu-graphs as the main medium. About 70% of =
> > class time=20
> > is spent in demonstrations. Complicated math is avoided. This format =
> > makes the=20
> > seminar more interesting to the students and helps them to achieve a =
> > deeper=20
> > understanding of the material covered. Many students have said that this =
> > was the=20
> > <I>best</I> technical seminar they ever attended! </P>
> > <P align=3Dleft> </P>
> > <P align=3Dleft>When: Dec 1 2000</P>
> > <P align=3Dleft>If you are interested then goto our weblink: <A=20
> > href=3D"http://www.ewh.ieee.org/r5/denver/rockymountainemc">http://www.ew=
> > h.ieee.org/r5/denver/rockymountainemc</A></P>
> > <P align=3Dleft>Look for the Dec 1 meeting link and sign up!!</P>
> > <P align=3Dleft>Charles Grasso<BR>Vice Chair=20
> > RMCEMCS</P></FONT></DIV></BODY></HTML>
> >
> > - ------=_NextPart_000_000C_01C03931.8EE7A3A0--
> >
> >
> >
> > **** To unsubscribe from si-list or si-list-digest: send e-mail to
> > [email protected]. In the BODY of message put: UNSUBSCRIBE
> > si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
> > si-list archives are accessible at http://www.qsl.net/wb6tpu
> > ****
> >
> > ------------------------------
> >
> > Date: Thu, 19 Oct 2000 11:44:46 -0800
> > From: sainath nimmagadda <[email protected]>
> > Subject: [SI-LIST] : SI - Salary Survey
> >
> > Hi SI folks:
> >
> > I understand that with growing complexity in multimedia technology, SI
> > positions are getting increasingly challenging (we see "PhD preferred"
> > in ads)and hopefully lucrative too. We often find salary surveys for
> > mainstream folks such as IT professionals. I am just curious if there is
> > some kind of salary survey for SI folks too. I am sure that helps us SI
> > folks have an idea where we stand in this dynamic market.
> >
> > Best,
> >
> > SN
> > _____________________________________________________________
> > Tired of limited space on Yahoo and Hotmail?
> > Free 100 Meg email account available at http://www.dacafe.com
> >
> >
> >
> > **** To unsubscribe from si-list or si-list-digest: send e-mail to
> > [email protected]. In the BODY of message put: UNSUBSCRIBE
> > si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
> > si-list archives are accessible at http://www.qsl.net/wb6tpu
> > ****
> >
> > ------------------------------
> >
> > Date: Thu, 19 Oct 2000 15:44:15 -0400
> > From: "zanella, fabrizio" <[email protected]>
> > Subject: [SI-LIST] : Differential TDR probes
> >
> > We're having problems getting a good high frequency launch when probing pc
> > boards and cable differential pairs when taking TDR measurements.Has
> anyone
> > found good differential TDR probes which allow you to measure very closely
> > spaced points on pc boards or cables?
> >
> > Thanks and regards,
> > Fabrizio Zanella
> > Hardware Engineering
> > EMC Corporation
> > [email protected]
> >
> >
> > **** To unsubscribe from si-list or si-list-digest: send e-mail to
> > [email protected]. In the BODY of message put: UNSUBSCRIBE
> > si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
> > si-list archives are accessible at http://www.qsl.net/wb6tpu
> > ****
> >
> > ------------------------------
> >
> > Date: Thu, 19 Oct 2000 14:12:22 -0700
> > From: "Ritesh Kapahi" <[email protected]>
> > Subject: Re: [SI-LIST] : Differential TDR probes
> >
> > Agilent has got some micro probe which is an accessory for their high
> > bandwidth scope 86100 and differential TDR module 54754A . It usually has
> a
> > long lead times (3-4 months)
> > Bye
> > Kaps
> >
> > - ----- Original Message -----
> > From: zanella, fabrizio <[email protected]>
> > To: SI List (E-mail) <[email protected]>
> > Sent: Thursday, October 19, 2000 12:44 PM
> > Subject: [SI-LIST] : Differential TDR probes
> >
> >
> > > We're having problems getting a good high frequency launch when probing
> pc
> > > boards and cable differential pairs when taking TDR measurements.Has
> > anyone
> > > found good differential TDR probes which allow you to measure very
> closely
> > > spaced points on pc boards or cables?
> > >
> > > Thanks and regards,
> > > Fabrizio Zanella
> > > Hardware Engineering
> > > EMC Corporation
> > > [email protected]
> > >
> > >
> > > **** To unsubscribe from si-list or si-list-digest: send e-mail to
> > > [email protected]. In the BODY of message put: UNSUBSCRIBE
> > > si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
> > > si-list archives are accessible at http://www.qsl.net/wb6tpu
> > > ****
> > >
> > >
> >
> >
> > **** To unsubscribe from si-list or si-list-digest: send e-mail to
> > [email protected]. In the BODY of message put: UNSUBSCRIBE
> > si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
> > si-list archives are accessible at http://www.qsl.net/wb6tpu
> > ****
> >
> > ------------------------------
> >
> > Date: Thu, 19 Oct 2000 16:39:38 -0500
> > From: [email protected]
> > Subject: Re: [SI-LIST] : Differential TDR probes
> >
> > Kaps,
> >
> > Have you comfirmed that the TDR Module 54754A works with their new 86100A
> main
> > frame?
> > They (their sales guys) tell me that it will not be ready until Dec 00.
> >
> > Thanks,
> > - -- Sal
> >
> >
> >
> >
> > "Ritesh Kapahi" <[email protected]> on 10/19/2000 04:12:22 PM
> >
> > Please respond to "Ritesh Kapahi" <[email protected]>
> >
> > Sent by: "Ritesh Kapahi" <[email protected]>
> >
> >
> > To: "zanella, fabrizio" <[email protected]>, "SI List
> > cc: (Salvador Aguinaga/MW/US/3Com)
> > Subject: Re: [SI-LIST] : Differential TDR probes
> >
> >
> >
> > Agilent has got some micro probe which is an accessory for their high
> > bandwidth scope 86100 and differential TDR module 54754A . It usually has
> a
> > long lead times (3-4 months)
> > Bye
> > Kaps
> >
> > - ----- Original Message -----
> > From: zanella, fabrizio <[email protected]>
> > To: SI List (E-mail) <[email protected]>
> > Sent: Thursday, October 19, 2000 12:44 PM
> > Subject: [SI-LIST] : Differential TDR probes
> >
> >
> > > We're having problems getting a good high frequency launch when probing
> pc
> > > boards and cable differential pairs when taking TDR measurements.Has
> > anyone
> > > found good differential TDR probes which allow you to measure very
> closely
> > > spaced points on pc boards or cables?
> > >
> > > Thanks and regards,
> > > Fabrizio Zanella
> > > Hardware Engineering
> > > EMC Corporation
> > > [email protected]
> > >
> > >
> > > **** To unsubscribe from si-list or si-list-digest: send e-mail to
> > > [email protected]. In the BODY of message put: UNSUBSCRIBE
> > > si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
> > > si-list archives are accessible at http://www.qsl.net/wb6tpu
> > > ****
> > >
> > >
> >
> >
> > **** To unsubscribe from si-list or si-list-digest: send e-mail to
> > [email protected]. In the BODY of message put: UNSUBSCRIBE
> > si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
> > si-list archives are accessible at http://www.qsl.net/wb6tpu
> > ****
> >
> >
> >
> >
> >
> >
> > **** To unsubscribe from si-list or si-list-digest: send e-mail to
> > [email protected]. In the BODY of message put: UNSUBSCRIBE
> > si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
> > si-list archives are accessible at http://www.qsl.net/wb6tpu
> > ****
> >
> > ------------------------------
> >
> > Date: Thu, 19 Oct 2000 17:26:16 -0500
> > From: "Daniel, Erik S." <[email protected]>
> > Subject: RE: [SI-LIST] : Differential TDR probes
> >
> > Fabrizio-
> >
> > A couple things we have used with some success for diff TDR on PC boards
> and
> > chip packages:
> >
> > 1. GGB Picoprobe Model 10
> > - --------------------------
> > These are micro-coax probes with needle-like tips connected at the end.
> > They are pretty cheap, and there are a wide variety of options (different
> > needle tip lengths, widths, materials, ...). We have used two
> ground-signal
> > style probes soldered together to form a GSSG style differential probe.
> The
> > needles are flexible and can be bent to accommodate different board
> > geometries (although bending the needles too much definitely degrades the
> > launch). There are some technical drawbacks to these, but they have come
> in
> > handy for troubleshooting.
> >
> > 2. GGB Picoprobe Model 40A Dual probes
> > - ---------------------------------------
> > These are very good microwave probes (with an advertised 40 GHz bandwidth)
> > that you can buy in GSSG or GSGSG styles in a variety of pitches. They
> are
> > fairly expensive, the lead times are long for custom orders, and I would
> not
> > recommend trying to bend these(!) to accommodate different geometries, but
> > they are electrically very good.
> >
> > There are a number of other similar microwave probes we have used in
> various
> > special cases, but I think I have used these two options the most.
> >
> > - Erik
> >
> > ==================================================================
> > Erik Daniel, Ph.D. Mayo Foundation
> > Voice: (507) 284-1634 Guggenheim 1011B
> > Fax: (507) 284-9171 200 First Street SW
> > E-mail: [email protected] Rochester, MN 55905
> > ==================================================================
> >
> >
> > > -----Original Message-----
> > > From: zanella, fabrizio [mailto:[email protected]]
> > > Sent: Thursday, October 19, 2000 2:44 PM
> > > To: SI List (E-mail)
> > > Subject: [SI-LIST] : Differential TDR probes
> > >
> > >
> > > We're having problems getting a good high frequency launch
> > > when probing pc
> > > boards and cable differential pairs when taking TDR
> > > measurements.Has anyone
> > > found good differential TDR probes which allow you to measure
> > > very closely
> > > spaced points on pc boards or cables?
> > >
> > > Thanks and regards,
> > > Fabrizio Zanella
> > > Hardware Engineering
> > > EMC Corporation
> > > [email protected]
> > >
> > >
> > > **** To unsubscribe from si-list or si-list-digest: send e-mail to
> > > [email protected]. In the BODY of message put: UNSUBSCRIBE
> > > si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
> > > si-list archives are accessible at http://www.qsl.net/wb6tpu
> > > ****
> > >
> >
> > **** To unsubscribe from si-list or si-list-digest: send e-mail to
> > [email protected]. In the BODY of message put: UNSUBSCRIBE
> > si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
> > si-list archives are accessible at http://www.qsl.net/wb6tpu
> > ****
> >
> > ------------------------------
> >
> > Date: Thu, 19 Oct 2000 15:38:44 -0700
> > From: John Fisher <[email protected]>
> > Subject: Re: [SI-LIST] : Differential TDR probes
> >
> > <html>
> > <font size=3>Fabrizio,<br>
> > <br>
> > We have built these using equal length sections of semi rigid coax with
> > sma's at one end. The semi rigid copper outer shield is soldered together
> > approx. every 3 ". Prepare the ends by careful cutting of the
> > shield with an exacto knife, than solder the center conductors to
> > the launch point vias or pads. Tektronix shipped some of these to
> > us as accessories when we bought their IPA-510 a few years ago. I
> > might be able to find a tek part number but someone like Micro-Coax could
> > make some for you or find an off the shelf semi rigid assembly with sma's
> > on both ends and then just cut it in half. Be carful not to bend it too
> > much and kink it. These can also make nice 50 Ohm 10x passive
> > probes with the addition of a series 450 resistor at the end.<br>
> > <br>
> > Regards<br>
> > <br>
> > John<br>
> > <br>
> > At 03:44 PM 10/19/00 -0400, you wrote:<br>
> > <blockquote type=cite cite>We're having problems getting a good high
> > frequency launch when probing pc<br>
> > boards and cable differential pairs when taking TDR measurements.Has
> > anyone<br>
> > found good differential TDR probes which allow you to measure very
> > closely<br>
> > spaced points on pc boards or cables?<br>
> > <br>
> > Thanks and regards,<br>
> > Fabrizio Zanella<br>
> > Hardware Engineering<br>
> > EMC Corporation<br>
> > [email protected]<br>
> > <br>
> > <br>
> > **** To unsubscribe from si-list or si-list-digest: send e-mail to<br>
> > [email protected]. In the BODY of message put:
> > UNSUBSCRIBE<br>
> > si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.<br>
> > si-list archives are accessible at
> > <a href="http://www.qsl.net/wb6tpu"
> eudora="autourl">http://www.qsl.net/wb6tpu><br>
> > ****</font></blockquote><br>
> >
> <div>*********************************************************************</
> div>
> > <div>John M. Fisher -- Cisco Systems -- [email protected]</div>
> > <div> 170 W. Tasman Dr., Bldg G, San Jose
> > CA 95134-1706</div>
> >
> <div><x-tab> </x-tab> &n
> bsp;
> > __
> >
> _ &nb
> sp;
> > _</div>
> > <div> ________/// \_/
> > \________/ \ ____</div>
> >
> <div><x-tab> </x-tab><x-tab>&
> nbsp; </x-tab><x-tab> &n
> bsp; </x-tab><x-tab> &nb
> sp; </x-tab>
> > \/</div>
> > <div>Manager Signal Integrity, Enterprise Line of Business</div>
> > <div>408-527-9186, Page 408-308-5501, Fax 408-526-5504,
> > N6PFN</div>
> > *********************************************************************
> > </html>
> >
> >
> > **** To unsubscribe from si-list or si-list-digest: send e-mail to
> > [email protected]. In the BODY of message put: UNSUBSCRIBE
> > si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
> > si-list archives are accessible at http://www.qsl.net/wb6tpu
> > ****
> >
> > ------------------------------
> >
> > End of si-list-digest V1 #286
> > *****************************
> >
> >
> > **** To unsubscribe from si-list or si-list-digest: send e-mail to
> [email protected]. In the BODY of message put: UNSUBSCRIBE si-list
> or UNSUBSCRIBE si-list-digest, for more help, put HELP.
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> > ****
>
> **** To unsubscribe from si-list or si-list-digest: send e-mail to
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This archive was generated by hypermail 2b29 : Tue May 08 2001 - 14:29:48 PDT