RE: [SI-LIST] : Attenuation on a PCB trace

About this list Date view Thread view Subject view Author view

From: Degerstrom, Michael J. (degerstrom.michael@mayo.edu)
Date: Fri Apr 13 2001 - 12:24:12 PDT


Khalid,

Borrowing from what Mike Conn said and what Paul Levin said
in a related response I can offer a start to your 'couple
of equations'. For 2.5Gbps your fundamental frequency
is a 1.25 Ghz sine wave. This will be attenuated by
a factor of exp(-alpha*Lo) where alpha = Real{(R+jwL)(G+jwC)}.
where RLCG are per unit length and Lo is the total length.
For a clock source you are probably fine just adding up
the contributions to the first several harmonics that comprise
a trapezoidal waveform that fits your clock source. It
is more complicated for data paths but we have done fft and
inverse fft on a PRBS signal to reconstruct an eye diagram.

RLCG are all functions of frequency. For most applications
C is fairly constant but you need to account for skin
effect for R, dielectric loss for G and internal inductance
for L. For some applications you have to look at phase
changes, i.e. the lower frequencies may propagate more
slowly than the higher frequencies. You can use
beta = Imag{(R+jwL)(G+jwC)} to determine if phase is
an important parameter.

I know that this is not much of a start but hopefully
there is enough to get you going.

Mike

_______________________________________________________________
Mike Degerstrom Email: degerstrom.michael@mayo.edu
Mayo Clinic; 200 1st Street SW ; Rochester, MN 55905
Phone: (507) 538-5462 FAX: (507) 284-9171
WWW: http://www.mayo.edu/sppdg/sppdg_home_page.html
_______________________________________________________________

> -----Original Message-----
> From: Khalid Ansari [mailto:khalida@vitesse.com]
> Sent: Thursday, April 12, 2001 4:29 PM
> To: Degerstrom, Michael J.; khalida@vitesse.com;
> si-list@silab.eng.sun.com
> Subject: RE: [SI-LIST] : Attenuation on a PCB trace
>
>
> What I meant was to pick up a couple of equations and
> estimate, without
> use of any tools.
>
> At 04:13 PM 4/12/01 -0500, Degerstrom, Michael J. wrote:
> >Khalid,
> >
> >Do you want to know how to simulate/calculate the loss
> >or how to go about measuring the loss? 'Measure theoretically'
> >is the term you used that confuses me.
> >
> >Mike
> >
> >_______________________________________________________________
> >Mike Degerstrom Email: degerstrom.michael@mayo.edu
> >Mayo Clinic; 200 1st Street SW ; Rochester, MN 55905
> >Phone: (507) 538-5462 FAX: (507) 284-9171
> >WWW: http://www.mayo.edu/sppdg/sppdg_home_page.html
> >_______________________________________________________________
> >
> >
> > > -----Original Message-----
> > > From: Khalid Ansari [mailto:khalida@vitesse.com]
> > > Sent: Thursday, April 12, 2001 1:33 PM
> > > To: si-list@silab.eng.sun.com
> > > Subject: [SI-LIST] : Attenuation on a PCB trace
> > >
> > >
> > > Hi all,
> > >
> > > Is there a way to measure theoretically what the attenuation
> > > of a signal will
> > > be after travelling 20" at say a frequency of 2.5 Gbps across
> > > a 50 ohms PCB
> > > trace
> > > laid out in FR4 in a microstrip configuration. How about in
> > > a stripline
> > > configuration?
> > > What are the factors that need to be taken in account to
> > > calculate this.
> > >
> > > Thanks in advance,
> > > Khalid
> > > ---
> > > Khalid Ansari
> > > Switch Fabric Applications
> > > Advanced Networking Products Division
> > > Vitesse Semiconductor Corp.
> > > 3408, Garrett Ave., Santa Clara, 95054
> > > Phone: (408) 986-4381 x144
> > > fax: (408) 986-6050
> > > http://www.vitesse.com
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > **** To unsubscribe from si-list or si-list-digest: send e-mail to
> > > majordomo@silab.eng.sun.com. 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
> > > ****
> > >
>
> ---
> Khalid Ansari
> Switch Fabric Applications
> Advanced Networking Products Division
> Vitesse Semiconductor Corp.
> 3408, Garrett Ave., Santa Clara, 95054
> Phone: (408) 986-4381 x144
> fax: (408) 986-6050
> http://www.vitesse.com
>
>
>
>
>
>
>
>
>
> **** To unsubscribe from si-list or si-list-digest: send e-mail to
> majordomo@silab.eng.sun.com. 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
majordomo@silab.eng.sun.com. 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
****


About this list Date view Thread view Subject view Author view

This archive was generated by hypermail 2b29 : Thu Jun 21 2001 - 10:11:35 PDT