[SI-LIST] Re: dielectric loss question

Jim

Could you share the data with me? I did some test recently. The
skin effect loss is not as bad as I expect at 10 Gbps data rate.

I have two pairs of differential traces with 100 ohms differential
impedance. One pair is microstrip line with 8 mils line width. The
second pair is stripline with 5 mils line width. The trace lengths
are 6" and 12" long for each pair. The eye patterns were took with=20
10 Gbps PRBS data pattern. The difference of eye patterns between=20
two pairs is  so small. It let me to believe that the skin effect=20
loss is not the significant part at 10 Gbps.

The roughness of copper sufface is two dimentional. One dimention
increase the length, which increases the resistance. And the other=20
dimention increase the perimeter of copper cross section, which
decreses the resistance. So, they should cancel each other. This
is just my 2 cents.

Regards!

Jinhua Chen
Consulting Design Engineer
176 South St.
Hopkinton, MA 01748
508-249-4527
Pager: 8779700234
chen_jinhua@xxxxxxx

EMC=B2 =20
The Enterprise Storage Company


-----Original Message-----
From: Jim G Roberts [mailto:jgroberts@xxxxxxxxxx]
Sent: Wednesday, February 12, 2003 9:23 AM
To: milabont@xxxxxxxxx
Cc: 'Si-List' (E-mail)
Subject: [SI-LIST] Re: dielectric loss question



Mike, Peter,
        It is also interesting that since data rate are in the 10GHz =
rates
that
the
surface roughness begins to give a large percentage of the losses.
These are also very frequency sensitive.
If of interest I have a PPT file.

--
Regards,    __________   James G Roberts
           /___  ____ |  jrobert@xxxxxxxxxxxxxxxxxxxxx
 Jim      __  / /___/ /  jgroberts@xxxxxxxxxx
         / /_/ /---| |   Room: BE436, Hilversum
         \____/    /_/   Tel: +31 35 687 4308 Fax: 5976

Mike LaBonte wrote:

> I don't have any info specific to moisture in PCBs. 2.45GHz
> is where the dielectric permittivity of water begins to decrease
> significantly, but it is not a peak absorption frequency. Peak
> dielectric loss for water occurs in the range of 10GHz to 160GHz,
> depending on the temperature. The peak frequency is higher for
> higher temperatures. At 25degC the peak is near 40GHz.
>
> At DesignCon 2000 Howard Johnson presented "Multi-Level Signaling",
> in which he gave the rate of change for signal degradation due to
> skin effect and dielectric loss at 20dB/decade near 1-2GHz. At
> least half of that is dielectric loss. But the paper also shows
> noise increasing at 20dB/decade, and SNR falling to zero under 10GHz.
>
> My take on it is that water will not be the main cause of signal
> loss.
>
> http://www.sbu.ac.uk/water/microwave.html
> http://signalintegrity.com/Pubs/misc/mls.htm
>
> Mike LaBonte
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
> [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Peter Arnold
> Sent: Tuesday, February 11, 2003 2:35 PM
> To: 'Si-List' (E-mail)
> Subject: [SI-LIST] dielectric loss question
>
> All,
>
> A question from the curious - in high-speed signaling environments we =
may
> create time-varying electric fields that have components close to the
> frequency used to heat water in microwave ovens, somewhere around =
2.45GHz.
> This suggests a portion of dielectric loss at these frequencies might =
be
due
> to dielectric heating of any moisture that might be present in the
> fiberglass.
>
> Is this in fact the case, and what magnitude is the effect at normal
> humidities? Does loss increase in real multi-GHZ signaling systems as
> dielectric moisture content increases?
>
> Thank you,
> peter arnold.
>
> ------------------------------------------------------------------
> 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:
> http://www.freelists.org/webpage/si-list
>
> For help:
> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>
> List archives are viewable at:
>                http://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:
> http://www.freelists.org/webpage/si-list
>
> For help:
> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>
> List archives are viewable at:
>                http://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:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field

List archives are viewable at:    =20
                http://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
------------------------------------------------------------------
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:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field

List archives are viewable at:     
                http://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: