Re: [SI-LIST] : About the AC analysis with HSPICE

Ray Anderson ([email protected])
Fri, 20 Aug 1999 12:41:55 -0700 (PDT)

Could it have something to do with the fact that your simulation
is driving the line from a zero impedance source while a real measurement
is driven from a finite impedance (50 ohms) ?

Try putting a 50 ohm series resistance between your voltage source and the
transmission line. Make your load resistor 50 ohms. Be sure to account for the
extra 6dB of voltage loss that the voltage division across the source resistor

-Ray Anderson
Sun Microsystems

> Hello,dear sir:
> These days I am busy doing the simulation to get the evaluation for loss of
> the transmission line.Generally,the loss increases with frequency
> increation.I find it difficult to get a satisfying result by doing the AC
> analysis with HSPICE.The reflections due to the high frequency are very
> terrific.What i did is:
> .options brief = 0
> .options scale = 1u
> V5 nd_pin1 gnd AC 1v
> .AC DEC 100.00 1K 1000MEG
> R1 cpin1 gnd 100
> Ws1 nd_pin1 gnd gnd cpin1 gnd gnd
> + Fsmodel=mother1 n=2 l=19000mil
> .material copper1 metal conductivity=5.96e+7 $inner
> .material copper2 metal conductivity=3.43e+7 $surface
> .material die_1 dielectric er=4.5 losstangent=1.7e-2
> conductivity=1.55e-7 .shape rect_1 rectangle
> width=10mil,height=1.38mil .layerstack stack_1 layer=(copper1,
> 1.38mil) layer=(die_1, 20mil ) layer=(die_1, 20.87mil ) layer=(copper1,
> 1.38mil) .Fsoptions wopt1 accuracy=high computegd=yes computers=yes
> computego=yes computero=yes printdata=yes gridfactor=3 *tline
> model(W_ELEMENT)
> .model mother1 w modeltype=FieldSolver,layerstack=stack_1,fsoptions=wopt1,
> + rlgcfile='hmbstrip42.rlgc'
> + conductor= (material =copper1, shape=rect_1,origin=(0mil, 21.38mil))
> + conductor= (material =copper1, shape=rect_1,origin=(18mil,21.38mil))
> *+ conductor= (material =copper1, shape=rect_1,origin=(28mil, 21.38mil))
> *+ conductor= (material =copper1, shape=rect_1,origin=(39mil,21.38mil))
> .PROBE AC VDB(cpin1,nd_pin1)
> .end
> From above ,you can know that I really use the 'AC sweep' analysis to get a
> curve which has the Y--20log[V(cpin1)/V(nd_pin1)],X--frequency.But the
> result is bad.I compared this result with the result i got by testing with
> network analysiser,the difference is terrifying! I don't think it a good way
> to evaluate transmission loss with AC analysis in HSPICE.Would you kind to
> recommend me a good way to evaluate transmission loss by SPICE simulation?
> Regards,
> Rachild

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