[SI-LIST] Re: Remove Ground underneath Differential signal isdeserved or not?
- From: Scott McMorrow <scott@xxxxxxxxxxxxx>
- To: leeritchey@xxxxxxxxxxxxx
- Date: Tue, 30 Jul 2002 00:11:55 -0700
Lee,
>What I show in my class is that guard traces are always LC networks that
>resonate at some frequency and can and do turn into bandpass filters at some
>frequencies. I demonstrate this will actual failed circuits.
>
>
This is exactly why Mike Conn and myself recommend stitching guard
traces to ground at random intervals across the length. The average
spacing of the via sites should be 1/10 of the wavelength of the fast
signal frequency or equivalent risetime that will be present on this
trace. These stitch vias to ground will eliminate the problems which
you have alluded to. They are backed by extremely good analytical and
experimental science.
Best regards,
Scott
--
Scott McMorrow
Teraspeed Consulting Group LLC
2926 SE Yamhill St.
Portland, OR 97214
(503) 239-5536
http://www.teraspeed.com
>Hope this helps.
>
>Lee
>
>Ibrahim Khan wrote:
>
>
>
>>Hello Ratchet man,
>>Nice to hear from you. Hope you will be contributing to this group on
>>regular basis. I took your class in Boston couple of years ago.
>>Last week there was a discussion about guard traces and I remember you
>>had a very strong opinion about them. Can you please share your
>>thoughts about the guard traces with this group.
>>
>>Regards
>>Ibrahim Khan
>>-----Original Message-----
>>From: Ritchey Lee [mailto:leeritchey@xxxxxxxxxxxxx]
>>Sent: Monday, July 29, 2002 11:07 AM
>>To: jian@xxxxxxxxxx
>>Cc: binchuan2000@xxxxxxxxxxxx; si-list@xxxxxxxxxxxxx
>>Subject: [SI-LIST] Re: Remove Ground underneath Differential signal is
>>deserved or not?
>>
>>Binchua,
>>
>>You don't ever want to remove the ground plane from underneath a
>>differnetial pair. Many more negative side effects result than the
>>alleged common mode energy might ever cause.
>>
>>Lee
>>
>>Jian X. Zheng wrote:
>>
>>
>>
>>>Hi, Binchuan:
>>>
>>>Removing the ground plane for differential pair will suppress the even
>>>
>>>
>>>mode. Basically, the even mode will not be propagating. Its energy
>>>will not be transmitted. The even mode signal, which is considered as
>>>noise, will be reduced in your circuit. Thanks!
>>>
>>>Best regards,
>>>
>>>----------------------------------------------------------------------
>>>-
>>>Jian-X. Zheng, Ph.D
>>>Zeland Software, Inc., 48890 Milmont Drive, 105D, Fremont, CA 94538,
>>>
>>>
>>U.S.A.
>>
>>
>>>Tel: 510-623-7162, Fax: 510-623-7135, Web: http://www.zeland.com
>>>---------------------------------------------------------------------
>>>
>>>
>>>
>>>>-----Original Message-----
>>>>From: si-list-bounce@xxxxxxxxxxxxx
>>>>[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of binchuan2000
>>>>Sent: Thursday, July 25, 2002 7:20 PM
>>>>To: si-list@xxxxxxxxxxxxx
>>>>Subject: [SI-LIST] Remove Ground underneath Differential signal is
>>>>deserved or not?
>>>>
>>>>
>>>>
>>>>I am confused that I read some book about remove Ground under
>>>>Differential could reduce the induced Current from Differential
>>>>pair, but the question is how we could control its
>>>>impedance(Differential
>>>>impedance) although Differential doesn't reference to Ground. If I
>>>>follow this content to REMOVE Ground under Differential pair how
>>>>could I control its Zodd impedance and its Zdiff impedance. Does it
>>>>will generate any other problem and if it does, why some textbook
>>>>advise it?
>>>>
>>>>Remove Ground is worth or not for Differential signal ?
>>>>
>>>>
>>>>
>>>>Thanks,
>>>>
>>>>
>>>>
>>>>Binchuan.Wang
>>>>
>>>>------------------------------------------------------------------
>>>>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
>>>>
>>>>
>>>>
>>>>
>>>------------------------------------------------------------------
>>>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
>>>
>>>
>>-- Binary/unsupported file stripped by Ecartis --
>>-- Type: text/x-vcard
>>-- File: vcard.vcf
>>-- Desc: Card for leeritchey@xxxxxxxxxxxxx
>>
>>------------------------------------------------------------------
>>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
>>
>>
>
>
>
>
>-- Binary/unsupported file stripped by Ecartis --
>-- Type: text/x-vcard
>-- File: vcard.vcf
>-- Desc: Card for leeritchey@xxxxxxxxxxxxx
>
>
>------------------------------------------------------------------
>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
>
>
>
>
>
------------------------------------------------------------------
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
Other related posts:
