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

Chan, Michael (Michael.Chan@COMPAQ.com)
Tue, 3 Aug 1999 09:35:35 -0500

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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