[SI-LIST] Re: Differences between HSPICE Field Solver and XTK Field Solver

There is a problem with the inductance calculation when using the internal
field solver in HSPICE....it is waaayyy off depending on what version you
are using.  Which brings up an interesting point....be sure you are aware of
the defects within the specific version of HSPICE you have.   

Heres a fun trick....

Take the lines below and run them once using the W element line and then
comment out the W and run with the U element line instead.  Then, plot the
s21 in Awaves for both.  They are supposed to be the same since they are
using the same model...but they aren't.  The funny thing is....not only are
they not the same...they are both wrong :>)  

...its not just the inductance that is incorrect in HSPICE....better be
aware of bugs in the "industry standard" tool we are using or the volume
control will soon change the channel :>)

****************************************************************************
*********
*Example
.option probe post
VIN in1 gnd AC=1V
.AC LIN 401 50MEG 20.05e9
Rs2 in2 GND 50  
Rload2 out2 gnd 50
Rload1 out1 gnd 1e14
*
w1 in1 in2 gnd out1 out2 gnd N=2 l=10 UMODEL=example
*u1 in1 in2 gnd out1 out2 gnd example l=10 
*
.model example u level=3 plev=3 elev=1 dlev=2 wlump=400 maxl=600
+ zk= 50 capl=42p clen=1 vrel=.7470 ra1=.022 d12=.088
+ fr1=2E9hz at1=1.3db   atlen=1
*
.fsoptions opt1 GRIDFACTOR=30, PRINTDATA=YES, COMPUTEGD=YES, COMPUTERS=YES
*
.net v(out1) vin rout=50 rin=50
.print ac  s21(db)
.end
****************************************************************************
********************

-----Original Message-----
From: tcoyle [mailto:TCoyle@xxxxxxxxxxxxxxxxxxxxxxx]
Sent: Wednesday, October 31, 2001 12:11 PM
To: si list
Subject: [SI-LIST] Differences between HSPICE Field Solver and XTK Field
Solver



Dear Si List,
I am using the microstrip equation in Howard Johnson's book to calculate
the impedance. So given a w=8mil, t=1.37mil, and h=21mil, I get an
impedance
of about 100 ohms. When I use the XTK field solver, I get an L=14.5nH
and a C=1.4pF. When I use the HSPICE field solver, I get an L=65nh and a
C=6.5pF.  They both give me an impedance of 100 Ohms but are quite
different values. I think the XTK values are correct, so I'm wondering
about the HSPICE field solver. Has anyone compared results between these
two tools?

Thanks

Tim


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