[SI-LIST] remove
- From: "Mohamed Mahmoud" <mahmoud.mohamed@xxxxxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Thu, 25 Jul 2002 14:13:50 -0700
FreeLists Mailing List Manager wrote:
>
> si-list Digest Wed, 24 Jul 2002 Volume: 02 Issue: 201
>
> In This Issue:
> [SI-LIST] Re: doubt about crosstalk.
> [SI-LIST] Re: doubt about crosstalk.
> [SI-LIST] Re: doubt about crosstalk.
> [SI-LIST] Re: doubt about crosstalk.
> [SI-LIST] dont understand
> [SI-LIST] Re: doubt about crosstalk.
> [SI-LIST] dont understand
>
> ----------------------------------------------------------------------
>
> Subject: [SI-LIST] Re: doubt about crosstalk.
> From: "Gregory R Edlund" <gedlund@xxxxxxxxxx>
> Date: Wed, 24 Jul 2002 08:32:21 -0500
>
> Yun,
>
> Good questions. Let me take a stab at the first question. You made the
> statement, "the ground guard line...has no influence on the magnetic
> field." Let's try a thought experiment. Consider two parallel microstrip
> lines WITHOUT a guard. Each line has a current flowing in it, a return
> current in the plane, and a corresponding magnetic flux loop formed by the
> current and it's return. Call these two loops Loop1 and Loop2. When
> current in Loop1 changes, it creates a change in magnetic flux through
> Loop2, and the changing flux induces a voltage on the second signal line.
> Now, imagine that you keep the two signal lines at the same spacing but
> introduce a ground guard trace between them. Because this guard trace is
> carrying some of the return current from signal 1 (and signal 2), it
> changes the shape of Loop1 and INTERCEPTS flux lines that would have
> crossed into Loop2 had the guard not been there, thereby lowering the
> induced voltage on the second signal line. Since there is no plane above
> the structure, some of the flux lines will still go over the top and wind
> up in Loop 2.
>
> So my conclusion is that a coplanar wave guide formed using a guard trace
> effects both the electric AND magnetic coupling. I won't comment on
> whether you're better off dropping the guard trace and using the same
> spacing; I would defer that answer to a good field solver. I have heard
> some folks say that the effective use of a guard trace is dependent on
> drilling vias in the guard trace at regular intervals. I've never
> investigated this myself.
>
> Greg Edlund
> Senior Engineer
> Signal Integrity
> IBM Engineering Solution Services
> 3605 Hwy. 52 N, Dept. HDC
> Rochester, MN 55901
> gedlund@xxxxxxxxxx
>
> Date: Tue, 23 Jul 2002 15:57:11 +0800
> From: yun <yunnan@xxxxxxxxxx>
> Subject: [SI-LIST] doubt about crosstalk.
>
> Hi,
> I encounted some doubt about crosstalk,hope someone can help me.
> 1.about ground guard line.
> To reduce long coplanar parellel's crosstalk,we can place a ground guard
> line between them.
> On my opinion,however,the ground guard line can only terminate the electric
> filed,it has no influnce
> on magnetic filed.As we know,the forward crosstalk nearly canceled because
> the negative polarity
> of electric filed couple and magnetic filed couple.So, the forward
> crosstalk will be larger when use
> the ground guard line than not use the ground guard line.
> 2.back to back return current crosstalk.
> The pcb layer configuration is sig1-gnd-sig2(just for describe
> question),then,both sig1 and sig2 layer's
> return currents will all on the same gnd layer.We know that the return
> currents will creat crosstalk on signal
> lines.So,will these return currents,created by each side of gnd
> layer,crosstalk?
> Thanks.
> yun
>
> ------------------------------
>
> Subject: [SI-LIST] Re: doubt about crosstalk.
> Date: Wed, 24 Jul 2002 14:13:45 -0500
> From: "Ibrahim Khan" <ikhan@xxxxxxxxxxxxxxxxxxx>
>
> Greg,
> I have a question here. If the return current is also flowing in the
> guard trace then hav'nt we basically increased the loop size on both
> traces.
>
> Thanks
> Ibrahim Khan
>
> -----Original Message-----
> From: Gregory R Edlund [mailto:gedlund@xxxxxxxxxx]=20
> Sent: Wednesday, July 24, 2002 8:32 AM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: doubt about crosstalk.
>
> Yun,
>
> Good questions. Let me take a stab at the first question. You made the
> statement, "the ground guard line...has no influence on the magnetic
> field." Let's try a thought experiment. Consider two parallel
> microstrip lines WITHOUT a guard. Each line has a current flowing in
> it, a return current in the plane, and a corresponding magnetic flux
> loop formed by the current and it's return. Call these two loops Loop1
> and Loop2. When current in Loop1 changes, it creates a change in
> magnetic flux through Loop2, and the changing flux induces a voltage on
> the second signal line. Now, imagine that you keep the two signal lines
> at the same spacing but introduce a ground guard trace between them.
> Because this guard trace is carrying some of the return current from
> signal 1 (and signal 2), it changes the shape of Loop1 and INTERCEPTS
> flux lines that would have crossed into Loop2 had the guard not been
> there, thereby lowering the induced voltage on the second signal line.
> Since there is no plane above the structure, some of the flux lines will
> still go over the top and wind up in Loop 2.
>
> So my conclusion is that a coplanar wave guide formed using a guard
> trace effects both the electric AND magnetic coupling. I won't comment
> on whether you're better off dropping the guard trace and using the same
> spacing; I would defer that answer to a good field solver. I have heard
> some folks say that the effective use of a guard trace is dependent on
> drilling vias in the guard trace at regular intervals. I've never
> investigated this myself.
>
> Greg Edlund
> Senior Engineer
> Signal Integrity
> IBM Engineering Solution Services
> 3605 Hwy. 52 N, Dept. HDC
> Rochester, MN 55901
> gedlund@xxxxxxxxxx
>
> Date: Tue, 23 Jul 2002 15:57:11 +0800
> From: yun <yunnan@xxxxxxxxxx>
> Subject: [SI-LIST] doubt about crosstalk.
>
> Hi,
> I encounted some doubt about crosstalk,hope someone can help me. 1.about
> ground guard line.
> To reduce long coplanar parellel's crosstalk,we can place a ground
> guard line between them. On my opinion,however,the ground guard line can
> only terminate the electric filed,it has no influnce on magnetic
> filed.As we know,the forward crosstalk nearly canceled because the
> negative polarity of electric filed couple and magnetic filed couple.So,
> the forward crosstalk will be larger when use the ground guard line than
> not use the ground guard line. 2.back to back return current crosstalk.
> The pcb layer configuration is sig1-gnd-sig2(just for describe
> question),then,both sig1 and sig2 layer's return currents will all on
> the same gnd layer.We know that the return currents will creat crosstalk
> on signal lines.So,will these return currents,created by each side of
> gnd layer,crosstalk? Thanks. yun
>
> ------------------------------------------------------------------
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> =20
>
> ------------------------------
>
> From: MikonCons@xxxxxxx
> Date: Wed, 24 Jul 2002 16:20:31 EDT
> Subject: [SI-LIST] Re: doubt about crosstalk.
>
> In a message dated 7/24/2002 6:37:22 AM Pacific Standard Time,
> gedlund@xxxxxxxxxx writes:
>
> > So my conclusion is that a coplanar wave guide formed using a guard trace
> > effects both the electric AND magnetic coupling. I won't comment on
> > whether you're better off dropping the guard trace and using the same
> > spacing; I would defer that answer to a good field solver. I have heard
> > some folks say that the effective use of a guard trace is dependent on
> > drilling vias in the guard trace at regular intervals. I've never
> > investigated this myself.
> >
>
> Guard traces are indeed very effective. I constructed, tested, and reported
> on the effects of guard traces way back in '89 as part of a seminar. A series
> of microstrips, guarded microstrips, striplines, and guarded striplines were
> constructed at specified 50 Ohm trace levels. The center-to-center spacing of
> the signal traces was maintained for all configurations and the trace widths
> adjusted to achieve the targeted 50 Ohm level for all lines. The LEAST
> beneficial effect for the guarded traces was observed (as expected) for
> microstrip. HOWEVER, the crosstalk was typically reduced by 14 dB and the
> radiated emissions by 6-8 dB. QED.
>
> I DID include vias spaced randomly (to avoid a ladder resonance) by 0.75 inch
> to 1.25 inch apart. For maximum effect, I believe the addition of vias to
> critical (not garden variety) signals will assure an improved isolation
> between signals. The added vias force "quiet ground" points along the signal
> path that can serve to better shield the critical signal traces.
>
> Mike
>
> Michael L. Conn
> Owner/Principal Consultant
> Mikon Consulting
>
> *** Serving Your Needs with Technical Excellence ***
>
> ------------------------------
>
> Date: Wed, 24 Jul 2002 13:28:56 -0700
> From: Val Mandrusov <valman@xxxxxxxxx>
> Subject: [SI-LIST] Re: doubt about crosstalk.
>
> Mike,
>
> Could you share the information of this study (1989) through SI people.
>
> Thanks
>
> At 16:20 24.07.2002 -0400, MikonCons@xxxxxxx wrote:
> >In a message dated 7/24/2002 6:37:22 AM Pacific Standard Time,
> >gedlund@xxxxxxxxxx writes:
> >
> >
> > > So my conclusion is that a coplanar wave guide formed using a guard trace
> > > effects both the electric AND magnetic coupling. I won't comment on
> > > whether you're better off dropping the guard trace and using the same
> > > spacing; I would defer that answer to a good field solver. I have heard
> > > some folks say that the effective use of a guard trace is dependent on
> > > drilling vias in the guard trace at regular intervals. I've never
> > > investigated this myself.
> > >
> >
> >Guard traces are indeed very effective. I constructed, tested, and reported
> >on the effects of guard traces way back in '89 as part of a seminar. A series
> >of microstrips, guarded microstrips, striplines, and guarded striplines were
> >constructed at specified 50 Ohm trace levels. The center-to-center spacing of
> >the signal traces was maintained for all configurations and the trace widths
> >adjusted to achieve the targeted 50 Ohm level for all lines. The LEAST
> >beneficial effect for the guarded traces was observed (as expected) for
> >microstrip. HOWEVER, the crosstalk was typically reduced by 14 dB and the
> >radiated emissions by 6-8 dB. QED.
> >
> >I DID include vias spaced randomly (to avoid a ladder resonance) by 0.75 inch
> >to 1.25 inch apart. For maximum effect, I believe the addition of vias to
> >critical (not garden variety) signals will assure an improved isolation
> >between signals. The added vias force "quiet ground" points along the signal
> >path that can serve to better shield the critical signal traces.
> >
> >Mike
> >
> >Michael L. Conn
> >Owner/Principal Consultant
> >Mikon Consulting
> >
> > *** Serving Your Needs with Technical Excellence ***
> >
> >
> >------------------------------------------------------------------
> >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 archives are viewable at:
> > //www.freelists.org/archives/si-list
> >or at our remote archives:
> > http://groups.yahoo.com/group/si-list/messages
> >Old (prior to June 6, 2001) list archives are viewable at:
> > http://www.qsl.net/wb6tpu
> >
>
> Val Mandrusov - Sr. Compliance Enginneer
>
> CISCO Systems, Inc
> 375 East Tasman Drive
> San Jose, CA 95134
> M/S SJ-06/04
> 408-853-7415 Phone
> 408-853-3872 FAX
>
> ------------------------------
>
> Subject: [SI-LIST] Re: doubt about crosstalk.
> Date: Wed, 24 Jul 2002 15:34:17 -0500
> From: "Ibrahim Khan" <ikhan@xxxxxxxxxxxxxxxxxxx>
>
> Mike,
> Can you please share your study with this group.
>
> Thanks
> Ibrahim Khan
>
> -----Original Message-----
> From: MikonCons@xxxxxxx [mailto:MikonCons@xxxxxxx]=20
> Sent: Wednesday, July 24, 2002 3:21 PM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: doubt about crosstalk.=20
>
> In a message dated 7/24/2002 6:37:22 AM Pacific Standard Time,=20
> gedlund@xxxxxxxxxx writes:
>
> > So my conclusion is that a coplanar wave guide formed using a guard=20
> > trace effects both the electric AND magnetic coupling. I won't=20
> > comment on whether you're better off dropping the guard trace and=20
> > using the same spacing; I would defer that answer to a good field=20
> > solver. I have heard some folks say that the effective use of a guard
>
> > trace is dependent on drilling vias in the guard trace at regular=20
> > intervals. I've never investigated this myself.
> >=20
>
> Guard traces are indeed very effective. I constructed, tested, and
> reported=20
> on the effects of guard traces way back in '89 as part of a seminar. A
> series=20
> of microstrips, guarded microstrips, striplines, and guarded striplines
> were=20
> constructed at specified 50 Ohm trace levels. The center-to-center
> spacing of=20
> the signal traces was maintained for all configurations and the trace
> widths=20
> adjusted to achieve the targeted 50 Ohm level for all lines. The LEAST=20
> beneficial effect for the guarded traces was observed (as expected) for=20
> microstrip. HOWEVER, the crosstalk was typically reduced by 14 dB and
> the=20
> radiated emissions by 6-8 dB. QED.
>
> I DID include vias spaced randomly (to avoid a ladder resonance) by 0.75
> inch=20
> to 1.25 inch apart. For maximum effect, I believe the addition of vias
> to=20
> critical (not garden variety) signals will assure an improved isolation=20
> between signals. The added vias force "quiet ground" points along the
> signal=20
> path that can serve to better shield the critical signal traces.
>
> Mike
>
> Michael L. Conn
> Owner/Principal Consultant
> Mikon Consulting
>
> *** Serving Your Needs with Technical Excellence ***
>
> ------------------------------------------------------------------
> 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 archives are viewable at: =20
> //www.freelists.org/archives/si-list
> or at our remote archives:
> http://groups.yahoo.com/group/si-list/messages=20
> Old (prior to June 6, 2001) list archives are viewable at:
> http://www.qsl.net/wb6tpu
> =20
>
> ------------------------------
>
> From: "Volk, Andrew M" <andrew.m.volk@xxxxxxxxx>
> Subject: [SI-LIST] Re: doubt about crosstalk.
> Date: Wed, 24 Jul 2002 14:05:36 -0700
>
> Mike -
>
> I'm sure of the effectiveness of the guard strip, especially with
> grounding vias, but vias require a lot of space. I was wondering
> if you did a control with the same layout without the guard trace
> and only used the spacing as the isolation?
>
> Regards,
> Andrew Volk
>
> -----Original Message-----
> From: MikonCons@xxxxxxx [mailto:MikonCons@xxxxxxx]
> Sent: Wednesday, July 24, 2002 1:21 PM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: doubt about crosstalk.
>
> In a message dated 7/24/2002 6:37:22 AM Pacific Standard Time,
> gedlund@xxxxxxxxxx writes:
>
> > So my conclusion is that a coplanar wave guide formed using a guard trace
> > effects both the electric AND magnetic coupling. I won't comment on
> > whether you're better off dropping the guard trace and using the same
> > spacing; I would defer that answer to a good field solver. I have heard
> > some folks say that the effective use of a guard trace is dependent on
> > drilling vias in the guard trace at regular intervals. I've never
> > investigated this myself.
> >
>
> Guard traces are indeed very effective. I constructed, tested, and reported
> on the effects of guard traces way back in '89 as part of a seminar. A
> series
> of microstrips, guarded microstrips, striplines, and guarded striplines were
>
> constructed at specified 50 Ohm trace levels. The center-to-center spacing
> of
> the signal traces was maintained for all configurations and the trace widths
>
> adjusted to achieve the targeted 50 Ohm level for all lines. The LEAST
> beneficial effect for the guarded traces was observed (as expected) for
> microstrip. HOWEVER, the crosstalk was typically reduced by 14 dB and the
> radiated emissions by 6-8 dB. QED.
>
> I DID include vias spaced randomly (to avoid a ladder resonance) by 0.75
> inch
> to 1.25 inch apart. For maximum effect, I believe the addition of vias to
> critical (not garden variety) signals will assure an improved isolation
> between signals. The added vias force "quiet ground" points along the signal
>
> path that can serve to better shield the critical signal traces.
>
> Mike
>
> Michael L. Conn
> Owner/Principal Consultant
> Mikon Consulting
>
> *** Serving Your Needs with Technical Excellence ***
>
> ------------------------------------------------------------------
> 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 archives are viewable at:
> //www.freelists.org/archives/si-list
> or at our remote archives:
> http://groups.yahoo.com/group/si-list/messages
> Old (prior to June 6, 2001) list archives are viewable at:
> http://www.qsl.net/wb6tpu
>
>
> ------------------------------
>
> From: MikonCons@xxxxxxx
> Date: Wed, 24 Jul 2002 17:56:31 EDT
> Subject: [SI-LIST] Re: doubt about crosstalk.
>
> Per multiple comments/requests:
>
> [Q] "I was wondering if you did a control with the same layout without the
> guard trace
> and only used the spacing as the isolation?"
>
> [Mikon] Yes. The reference point for performance was precisely what you
> describe. As I originally stated, "A series of microstrips, guarded
> microstrips, striplines, and guarded striplines were constructed at specified
> 50 Ohm trace levels. The center-to-center spacing of the signal traces was
> maintained for all configurations and the trace widths adjusted to achieve
> the targeted 50 Ohm level for all lines."
>
> [Q] "There are two components to crosstalk, magnetic and capacitive. I can
> see
> where a guard trace can easily help with the capacitive crosstalk but the
> effects on magnetic crosstalk would be much less. The magnetic field contains
> energy in the flux lines. It is unclear to me whether the magnetic crosstalk
> can
> be lowered by placing a parasitic loop between the aggressor and the victim
> traces.
>
> [Mikon] The guard traces (as well as the ground planes) carry high frequency
> return currents (i.e., in the opposite direction) induced by the signals and
> help reduce the magnetic loop and the field intensities created thereby.
>
> [Q] "Can you please share your study with this group."
>
> Actually, I thought I just did share my results, at least about the crosstalk
> question. In the same tutorial, I also introduced the multiple-layer,
> co-planar, via-connected, chassis ground trace techniques for reduction of
> edge-related radiated emissions (and superior ESD protection), multiple other
> radiation and crosstalk reduction techniques, and a dissertation on buried
> capacitance versus discrete capacitors for power distribution system
> decoupling. The full tutorial is over an hour long and has long since been
> archived in my files. It was also in a different presentation format than the
> now more common Microsoft PowerPoint files.
>
> You might try to access the files at Hewlett-Packard (now Agilent) as that
> work is published multiple times in the 1990 to 1993 HP High-Speed Design
> Seminar books. They also did a videotape of my associated presentation which
> was marketed (via a third party) out of either San Antonio or Houston, Texas
> (I don't precisely recall which).
>
> The most recent publication I know of is in both the U.S. and European HP
> seminar books "1993 High Speed Digital Design Symposium." At that time, Jim
> Kabel was the Test and Measurement U.S. Marketing Center Manager for HP. You
> might try to locate more information through him.
>
> That's all I have time for now, so good luck.
>
> Mike
>
> Michael L. Conn
> Owner/Principal Consultant
> Mikon Consulting
>
> *** Serving Your Needs with Technical Excellence ***
>
> ------------------------------
>
> Date: Thu, 25 Jul 2002 08:44:59 +0800
> From: qzheng <qzheng@xxxxxxxxxxxxxxxx>
> Subject: [SI-LIST] dont understand
>
> Hello si-list,
>
> I dont understand the meaning of "ladder resonances" ?? who can
> help
>
> thanks
>
> --
> Best regards,
> qzheng mailto:qzheng@xxxxxxxxxxxxxxxx
>
> ------------------------------
>
> From: "Ismail B - CTD, Chennai." <ismailb@xxxxxxxxxxxxxxx>
> Subject: [SI-LIST] Re: doubt about crosstalk.
> Date: Thu, 25 Jul 2002 10:42:26 +0530
>
> >[Mikon] The guard traces (as well as the ground planes) carry high
> frequency
> >return currents (i.e., in the opposite direction) induced by the signals
> and
> >help reduce the magnetic loop and the field intensities created thereby.
>
> Mike, your's is a good explanation. In my opionion the ground planes carry
> the same
> high frequency return currents as the signal traces, but in an opposite
> direction.
> Hence the magnetic field created by the ground strips should oppose the
> magnetic
> field produced by the signal traces, thereby reducing the degree of
> coupling.
>
> Regards,
> Ismail
>
> ------------------------------
>
> From: MikonCons@xxxxxxx
> Date: Thu, 25 Jul 2002 01:19:09 EDT
> Subject: [SI-LIST] dont understand
>
> Qzheng:
>
> Sorry about the confusion. I refer to an equally spaced row of vias as
> representing a "ladder" with repetitive rungs. Such a structure will have a
> common resonant frequency for each of the rung segments; therefore, I choose
> to stagger the spaces between vias to detune possible reinforcement of a
> given resonance.
>
> Mike
>
> Michael L. Conn
> Owner/Principal Consultant
> Mikon Consulting
>
> *** Serving Your Needs with Technical Excellence ***
>
> ------------------------------
>
> End of si-list Digest V2 #201
> *****************************
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