FreeLists / si-list / [SI-LIST] single RLC parameters at a certain frequency

[xuzhengrong <Zhengrong.Xu@xxxxxxxxxx>]

Hi,
To simplify the model, we often extract single RLGC parameters from the
s-parameter model at a certain frequency.
I wonder what on earth the meaning of the single frequency parameters is.
First, if the parameters only represent the magnitude and phase of the
S-parameter model at the frequency point, it may have different combinations
of RLGC to reach the same goal, what's the method or principle?
Second, if the parameters are meaningful at a certain frequency, why can
single RLGC parameters often be used to estimate characteristic of package
model such as IBIS?  

In my opinion, for example, the single RLGC model should be the first-order
approximation to the real model for transmission line, as Eric's book
'Signal Integrity: Simplified' said.
It is equivalent to the real model within low frequency range and we can use
it if the signal frequency component is within the range.
However, if the RLGC model extracted at a certain frequency is only
meaningful for the extracting frequency, it isn't the first-order
approximation for the transmission line.
So we can't use it as the first-order approximation and estimate its low
frequency characteristic. 


Appreciate any idea and discussion for the problem.

Best Regards,
Zhengrong 

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