[SI-LIST] Re: Simple H-Spice Question
- From: "gsletch" <gsletch@xxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Tue, 08 Feb 2005 20:17:49 -0000
Yea...I have noticed a difference in how H-Spice models a lossless
T-Line and a Lossy T-Line. They seem to model a lossless line as one
lumped element only...no LC component.
I thought to determine if a interconnect is to be modeled lumped vs.
segmented was to check the wavelength of the highest freq. of interest
and divide by 10...if this number is greater than the interconnect
length of interest, then you can model the interconnect of interest as
one lumped LC element. And the other way around, you model it as a
number of segments...LC for lossless and RLCG if lossy...with the
number of segments >= 10 * ((length of the
interconnect)/(Risetime)*(vprop))
H-Spice doesn't give you the segmented option for a lossless
line...maybe your only choice is to use the U-line model(lossy), but
remove the resistive/conductive(RG) components, so you get basically a
lossless, segmented T-Line???? I am a little confused....
--- In si-list@xxxxxxxxxxxxxxx, "Andrew Ingraham" <a.ingraham@xxxx>
wrote:
> The lossless transmission line model (and I thought this applied to
HSpice
> as well) is not divided up into L/C segments. It is one atomic
element. It
> is effectively implemented as two pure delays (one in each
direction), with
> some resistors and controlled sources at the ends. The model
doesn't
> contain any capacitors or inductors.
>
> I don't believe there is any benefit to dividing one up into
multiple
> identical sections.
>
> This ought to work:
>
> > T1 100 0 180 Z0 = 70.7 TD = 7070p
>
> Now if it were a lumped model to start with, perhaps a lossy line
model,
> then I can see where you might want to control the number of lumps.
>
> Regards,
> Andy
>
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