Re: [SI-LIST] : Attenuation and Delay on a PCB Trance

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From: Abdulrahman Rafiq ([email protected])
Date: Mon Apr 16 2001 - 12:50:45 PDT

I have the same question--I am new member on the list and was wondering if
there is a news group I can point my mail program to as I am getting to many
emails

Thanks

Chuck Reynolds wrote:

> Hi all - where do I point to, to setup to get these emails as a NEWS group
> instead of emails?
> Thanks
>
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]]On Behalf Of Degerstrom, Michael
> J.
> Sent: Friday, April 13, 2001 9:31 AM
> To: [email protected]; [email protected]
> Subject: RE: [SI-LIST] : Attenuation and Delay on a PCB Trance
>
> Paul,
>
> I've noticed that w-element eye-diagram simulations show
> very minimal jitter whereas your statements below suggest
> to me that there should be jitter due to the internal inductance
> effect. I haven't used the HSPICE w-element model for
> a year or so but I have a technique to extract RLCG as
> a function of frequency and the inductance was flat. I haven't
> tried this yet for the new HSPICE w-element model with tabulated
> RLCG vs. frequency.
>
> I haven't directly looked into the lossy line equations but
> in working with someone who has my impression was that the 1+j
> factor was needed to provide a causal response. Also I thought
> that the HSPICE w-element lossy line algorithm used the
> 1+j but it somehow does not affect the inductance versus frequency.
>
> Mike
>
> _______________________________________________________________
> Mike Degerstrom Email: [email protected]
> 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: Paul Levin [mailto:[email protected]]
> > Sent: Thursday, April 12, 2001 6:32 PM
> > To: [email protected]
> > Subject: [SI-LIST] : Attenuation and Delay on a PCB Trance
> >
> >
> > To all concerned,
> >
> > Besides the attenuation effects on PCB traces, don't forget that the
> > propagation
> > delay is a function of frequency EVEN IF EPSILON-R IS CONSTANT.
> >
> > Few people realize that skin effect resistance is only a
> > portion of the
> > skin effect
> > impedance. The Rs figure must really be multiplied by (1+j). This
> > inductive
> > reactance means that there is a bit more inductance
> > (diminishing as the
> > frequency
> > increases.) Because of this, lower frequencies propagate more slowly
> > than
> > higher frequencies.
> >
> > This effect has nearly disappeared by the time one gets to 1
> > GHz, but 1
> > and 2
> > Gbps data signals have frequency components much lower than a GHz.
> > Consider
> > Fibre Channel's "alternating disparity K28.5 pattern." This 20 bit
> > pattern has
> > quite a bit of energy at 1/20th of the data rate. Some others
> > have told
> > me that
> > they have been able to create some (admittedly pathological) data
> > patterns
> > that resulted in even lower frequency content.
> >
> > Some years ago I computed the Fourier transform of the entire pattern
> > and
> > ran the harmonics through both the attenuation and phase
> > characteristics
> > of
> > microstrip. It surprised people how well I could simulate the
> > asymmetrical
> > eye pattern. The analysis worked for shielded, twisted pair, too.
> >
> > Paul Levin
> > Senior Principal Engineer
> > Logic Innovations, Inc.
> > A Xyratex Company
> >
> >
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--
*********************************************************************
Abdulrahman A. Rafiq (AKA Abbey)
Hardware/Layout Engineer

CISCO SYSTEMS INC.
Signal Integrity and Packaging Group
230 West Tasman Drive
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San Jose, Ca 95134
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