[SI-LIST] Re: W Model for transmission lines

Here is the diff pair model.  You may want to adjust 
your copper/fr4 thickness and conductor shape based on
feedback from your fab vendor.

----------------Cut Here ---------------------------

********** W element tline definition**********
*
* The following defines a two conductor w
* element transmission line model for a dual
* stripline board structure with 0.5 oz trace
* thickness, 4 mil wide trace and 60 ohm target
* characteristic impedance. The six mil separation
* between the traces produces a diff impedance of 
* 99.2 ohms.  This was calculated using the Polar
* Instruments CITS25 Field Solver. This will model one
* coupled differential signal pair.

* Define the board material
.MATERIAL diel_fr4 DIELECTRIC ER=4.1
+LOSSTANGENT=0.020
.MATERIAL copper METAL CONDUCTIVITY=5.8e+07

* Define the cross section of the trace, rectangle
* 1/2 oz copper, 4 mil wide
.SHAPE rect RECTANGLE WIDTH=4mil, HEIGHT=0.7mil

* Define the dual stripline structure, two striplines
* between two 2 oz pwr/gnd planes. Each trace is 5 mils
* from the plane and five mils from the other trace.

.LAYERSTACK dual_sl_60,
+ LAYER= (copper,2.8mil), LAYER=(diel_fr4,16.4mil),
+ LAYER= (copper,2.8mil)

.FSOPTIONS opt1 PRINTDATA=YES
+ ComputeRo=yes ComputeRs=yes ComputeGo=Yes ComputeGd=yes
+ ACCURACY = HIGH

.MODEL cond2_diff W MODELTYPE=Fieldsolver,
+LAYERSTACK=dual_sl_60, FSOPTIONS=opt1,
+RLGCFILE=cond2diff.rlgc,
+CONDUCTOR= (MATERIAL=copper, SHAPE=rect, ORIGIN= (0, 7.8mil)),
+CONDUCTOR= (MATERIAL=copper, SHAPE=rect, ORIGIN= (10mil, 7.8mil))

******  End of the W element definition
******************************************************

* Example
* define a 4 inch instance of the w element stripline
* illustrated above.

*W1 lvdsout1a lvdsout1b 0 OUTA OUTB 0 FSmodel=cond2_diff
*+N=2 l=4000mil

------------------ Cut Here Too ----------------------------------

-----Original Message-----
From: Greim, Michael [mailto:mgreim@xxxxxxxxxxxx]
Sent: Monday, September 24, 2001 8:26 AM
To: 'richard2636@xxxxxxxxxx'; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: W Model for transmission lines


Hi Richard,

It is possible to create the W model from the 
trace geometries and material properties.  This
is outlined pretty well in the avanti hspice 
manual within the Using Transmission Lines chapter
(chapter 19 I believe).  You can recreate the 
structure and use the internal field solver to 
create what you need.  I have included two pretty 
well commented models that you can use as a refer
ence along with this chapter to get you moving.
One is a single ended line and one is a coupled 
model.  The later can be used as a diff pair or to
show the effects of coupling between two single 
ended connectors. 

Best of Luck and happy HSpicing.  Feel free to 
drop me a line if you have any other questions.

best regards,

Michael Greim

-----Original Message-----
From: richard hill [mailto:richard2636@xxxxxxxxxx]
Sent: Saturday, September 22, 2001 8:52 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] W Model for transmission lines



Hi,

I am new to the use of transmission line models
in HSPICE.  I would like to create a W Model of
a transmission line.  I am wondering how to derive 
the RLGC parameters to incorporate it in my models.
I am struggling with this since it is not easy as the
U model where you just enter the trace geometry.  If
I know the trace geometry is there an easy way to get
the parameters.

Thanks.





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