RE: [SI-LIST] : Proposal: Rs correlation/collaboration for W-Elem

Mellitz, Richard (richard.mellitz@intel.com)
Wed, 4 Aug 1999 07:01:10 -0700

Michael,

Were you including a lossy ground plane?

Richard Mellitz
Intel

-----Original Message-----
From: Chan, Michael [mailto:Michael.Chan@COMPAQ.com]
Sent: Tuesday, August 03, 1999 10:36 AM
To: 'si-list@silab.eng.sun.com'
Subject: RE: [SI-LIST] : Proposal: Rs
correlation/collaboration for W-Elem ents

Richard:
The DC resistance ( R0 ) from Simpest is 4.519685
Ohms/meter.

I believe the value is the asymptotic skin-effect resistance
and this
should equal to Rs as used by W-element as you can see the
unit is
ohms/sqrt(Hz)*meter. This is not R(f)!! I will double check
with Michael
Tsuk in this case as my user manual miss the section
description on
resistance matrix. I am not sure whether it is real or the
magnitude but
since
the 2-D software is based on boundary-element method

Pacific Numerix's calculation will give R(f) and then Rs has
to be
calculated
using the equation as you described as below or from the
Hspice manual. That
is normally what I do when I generate lossy W-element
transmission lines for
Hpsice 98.2 and 98.4.
Unfortunately we have retired our Silicon Graphic server and
so I cannot run
that software to double check everything at this moment. I
will try to run
FastHenry to check what the number looks like this afternoon
and let you
know.

The result from Ray Anderson of Sun shows Rs for different
frequencies from
Applied Simulation Tech. and I don't know whether the
software reports Rs
directly or R(f) and Ray calculate those numbers manually
using the below
equation. I speculate if I use the same frequencies as Ray
used in Pacific
Numerix, the result would not be that far off. The only
concern I have is
his number at 1MHz. At 1MHz, the skin depth is 2.6mils which
is larger than
the thickness of your conductor ( 1mil ) and so Rs at 1MHz
should be smaller
than at 1GHz as point out by Ray.

Regards,
Michael Chan
Compaq Computer Corp.

-----Original Message-----
From: Mellitz, Richard [mailto:richard.mellitz@intel.com]
Sent: Tuesday, August 03, 1999 7:41 AM
To: 'si-list@silab.eng.sun.com'
Subject: RE: [SI-LIST] : Proposal: Rs
correlation/collaboration for
W-Elem ents

Michael,

Is this the real or magnitude of Rs? Did you subtract the DC
Ro value out?

i.e. if the intrinsic resistance of a line as function of
frequency behaves
as follows:

Rline(f)= R0 + Rs sqrt(f)

Then,
Rline(f) - R0
Rs = ------------------
sqrt(f)

I believe for our example R0 is 4.449 ohms/meter.

Regards,
Richard Mellitz,
Intel

PS I have SIMPEST cup. :-)

-----Original Message-----
From: Chan, Michael
[mailto:Michael.Chan@COMPAQ.com]
Sent: Monday, August 02, 1999 7:00 PM
To: 'si-list@silab.eng.sun.com'
Subject: RE: [SI-LIST] : Proposal: Rs
correlation/collaboration for W-Elem ents

I ran Richard's microstrip example under
SIMPEST 3.1 ( DEC's
in-house
developed
tool ) and came up with the following
result:

HF Resistance: 1.3555e-3
Ohms/(sqrt(Hz).meter)

Regards,
Michael Chan
Compaq Computer Corp.

-----Original Message-----
From: Ray Anderson
[mailto:raymonda@radium.eng.sun.com]
Sent: Monday, August 02, 1999 12:44 PM
To: si-list@silab.eng.sun.com
Subject: Re: [SI-LIST] : Proposal: Rs
correlation/collaboration for
W-Elements

I ran Richard's microstrip example under
Apsim RLGC 1.500.0
(a spectral
domain solver) and came up with the
following results:

Evaluated @ Re(Rs)
-----------
--------------------------------
@1MHz 1.4874E-3
Ohms/(sqrt(Hz)*meter)
@100MHz 1.0933E-3
Ohms/(sqrt(Hz)*meter)
@1GHz 1.2272E-3
Ohms/(sqrt(Hz)*meter)
@5GHz 1.3207E-3
Ohms/(sqrt(Hz)*meter)

The value at 1 MHz is curious in that it is
larger than the
values at higher frequencies which seem to
fall on a
frequency
dependent monotonic line.

Ray Anderson
Sun Microsystems Inc.

> I would like to make a proposal. I would
like to know what
various field
> solvers report in regards to the above
propagation
function. Let's start
> with a microstrip first (and only look at
skin effect).
The geometry
> follows.
>
> Height over ground: 0.004"
> Width of conductor: 0.006"
> Thickness of conductor: 0.001"
>
> Conductivity: 0.58E8 mho/meter
>
> Let's all use the same units for Rs. Say:
> Ohms/(sqrt(Hz)*meter)
>
> Now, A colleague of mine has supplied a
formula that is
used in microwave
> design. I have attached a PDF file with
details. (Too
tough for text, TTFT
> :-)), I remember foobar)
>
> The answer, using the closed form formula
for Rs is:
> 1.806E-03 ohms/(sqrt(Hz)*meter)
>
> If this is the magnitude of complex Rs,
then Re(Rs) would
be
> 1.277E-03 ohms/(sqrt(Hz)*meter)
>

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