RE: [SI-LIST] : RE: RESULTS to Proposal: Rs correlation/collaboration for W-Elements

Craig Callen (ccallen@ibnets.com)
Thu, 5 Aug 1999 12:07:09 -0400

I am currently using XFX from QUAD and you must multiply
Rs by sqrt(2*pi) for Gd you must multiply by (2*pi).

Results for microstrip:
XFX Lambda=1:
Rs=1.105e-3 Ohms/(sqrt(Hz).meter)
Rdc=4.38 Ohms/meter

XFX Lambda=1.5:
Rs=1.353e-3 Ohms/(sqrt(Hz).meter)
Rdc=4.38 Ohms/meter

I think the surface roughness factor of lambda=6 is quite large.

Craig Callen
Ironbridge Networks

> -----Original Message-----
> From: owner-si-list@silab.eng.sun.com
> [mailto:owner-si-list@silab.eng.sun.com]On Behalf Of Mellitz, Richard
> Sent: Wednesday, August 04, 1999 5:03 PM
> To: 'si-list@silab.eng.sun.com'
> Subject: [SI-LIST] : RE: RESULTS to Proposal: Rs
> correlation/collaboration for W-Elements
>
>
> I think I've got to augment my table. Apparently XFX reports Rs
> in terms of
> radians. If we multiply the Rs from XFX (with lambda = 1) times the
> sqrt(2*pi) we get: Rs=1.314E-3 Ohms/(sqrt(Hz).meter) which is roughly the
> same as every one else. The farthest one off of the group seems to be the
> HSPICE field solver.
>
> So this means if you used XFX to determine Rs for HSPICE,, you need to
> multiply the Rs value (in the tlp file) by the sqrt(2*pi).
>
> I still don't have a good answer for ground plane losses yet. I
> have someone
> using yet another modeler to do both lossy and lossless ground
> plane. I'll
> post a new table one I get some new data.
>
> Richard Mellitz
> Intel
>
> -----Original Message-----
> From: Mellitz, Richard
> Sent: Wednesday, August 04, 1999 1:13 PM
> To: 'si-list@silab.eng.sun.com'
> Subject: RESULTS to Proposal: Rs
> correlation/collaboration for W-Elements
>
> Rs Tabulations so far (8/4/99):
> ______________________________
>
> Equation: signal + ground
> Rs= 1.806e-3 Ohms/(sqrt(Hz).meter)
> Equation: signal alone
> Rs= 1.455e-3 Ohms/(sqrt(Hz).meter)
> R0= 4.454 Ohms/meter
> SIMPEST (COMPAC)
> Rs= 1.3555e-3 Ohms/(sqrt(Hz).meter)
> RO= 4.519685 Ohms/meter
> AP SIM
> Rs= 1.245e-3 Ohms/(sqrt(Hz).meter)
> R0= 5.346 Ohms/meter
> Quad Design's XFX (universe =50 mils, Lambda =1, Integral
> Mode)
> Rs= 5.241E-4 Ohms/(sqrt(Hz).meter)
> R0= 4.456 Ohms/meter
> Quad Design's XFX (universe =50 mils, Lambda =6, Integral
> Mode)
> Rs= 1.284E-3 Ohms/(sqrt(Hz).meter)
> R0= 4.456 Ohms/meter
> HSPICE 98.4 field solver
> RS= 7.26284e-04 Ohms/(sqrt(Hz).meter)
> RO= 4.37069 Ohms/meter
>
> It looks like SIMPEST, AP SIM, XFX lambda=6, and Rs equation
> for the signal line are all close.
>
> Questions to resolve for accurate W element usage.
> 1) Should Rs include return plane skin effects? Michael Chan used a PEC
> in SIMPEST and because it seems close to others, I might assume the other
> did not include ground losses.
> 2) Why do I need to set lambda= 5 to 6 in Quad Designs XFX to get Rs
> results that are similar to other modeling programs?
>
> Richard Mellitz,
> Intel
>
> -----Original Message-----
> From: Mellitz, Richard
> [mailto:richard.mellitz@intel.com]
> Sent: Monday, August 02, 1999 10:51 AM
> To: 'si-list@silab.eng.sun.com'
> Subject: [SI-LIST] : Proposal: Rs
> correlation/collaboration for W-Elements
>
> << File: Mathcad - ms_loss_eq.pdf >>
> Apparently the W element model uses a
> pseudo-propagation function with the following form.
> P(f)= exp{-sqrt[
> (G0+f*Gd+j*2*pi*f*C)*(R0+sqrt(f)(1+j)Rs+j*2*pi*f*L) ]*len }
>
> (From HSPICE application note "Boosting
> Accuracy of W Element for Transmission Lines with Nonzero Rs or
> Gd Values")
> Let's assume that this is valid for some
> conditions. It would be nice to know what the assumptions are.(geometry,
> frequency, etc.) We can talk about the validity of the above in another
> thread.
> 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)
> I have received sidebar results from some of
> you folks, but I don't want to post other people answers. However I will
> compile a table of posted results. There are issues of complex number
> involved. Remember I'm looking for the Rs for the above propagation
> formula.
>
> Step 2 will be to do same for a strip line
> geometry where:
> Height over ground: 0.005"
> Width of conductor: 0.0025"
> Thickness of conductor: 0.0005"
> Distance between ground planes: 0.0105
>
>
> It would be appreciated if we could find out
> what "tricks" people are using to get Rs from their field solvers.
> Regards,
> Richard Mellitz
> Intel
>
> <<Mathcad - ms_loss_eq.pdf>>
>
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