Re: [SI-LIST] : HSPICE transmission line modelling

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From: Mike Degerstrom (degerstrom.michael@mayo.edu)
Date: Mon Nov 15 1999 - 06:30:38 PST


Qu Pingyu,

There are two things I see wrong with your HSPICE s-parameter setup.
First you are trying to compute s-parameters for a current. This
doesn't make sense. You know by definition that the current is really
your (voltage) s-parameters divided by the port impedance which you have chosen
to be 50 ohms. Secondly, the port 2 should be left as a high impedance
to ground whereas you have a voltage source at port 2. To satisfy
HSPICE that doesn't like floating nodes I will typically tie a 100K
resistor from port 2 to ground. The HSPICE s-parameter (.net statement)
automatically assumes that 'rout=50' is your port 2 impedance.

I haven't used the 'ELEV' option so I can't comment further.

Good luck,

Mike

On Nov 15, 1:53pm, Qu Pingyu wrote:
> Subject: [SI-LIST] : HSPICE transmission line modelling
> Hello, everyone:
>
> I'm learning to use HSPICE for transmission line modelling. As a start, I
> tried to run a S parameter simulation of a simple U element TL with
> precomputed RLCG value for testing. However, the simulation results are
> wrong. I guess I make some mistakes in the input file. Can anyone gave me
> some suggestions ?
>
> Also, when I use ELEV = 2 which specify the "precomputed RLCG" case, I was
> prompted by the software that I have to define PLEV value, i.e, the geometry
> type of the transmission line. Why is that ? I thought with precomputed
> RLCG, SPICE will not bother the geometry the transmission line, isn't it?
>
> Here is my input file:
>
> .option list post
> .net i(vout) vin rout=50 rin=50
> .ac lin 100 100meg 10g
> .print s11(db) s21(db)
> *.graph s11(mag) s21(mag)
> *.graph s21(phase) s11(phase)
>
> vout out 0 0v
> vin in 0 ac=1 dc=0v
>
> u1 in gnd out gnd fr4 l=1400mil
>
> .model plateline U LEVEL=3 PLEV=1 ELEV=2 NL=1 LLEV=0
> + cr1=300P L11=351.86N r11=20
>
> .end
>
> Thanks in advance for your reply.
>
> Best Regards
>
> Qu Pingyu
>
> Institute of Microelectronics
> 11 Science Park Road, Singapore
>
> DID: 65-7705413
> Fax: 65-7745747
>
>
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>-- End of excerpt from Qu Pingyu

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