[SI-LIST] Re: lumped model vs distributed model

  • From: "Abe Riazi" <ARIAZI@xxxxxxxxxxx>
  • To: <si-list@xxxxxxxxxxxxx>
  • Date: Tue, 4 Dec 2001 21:51:01 -0800

Steve Corey Wrote:

>  I don't own Hall's book, but I would presume that the
> analysis was done assuming constant RLGC parameters.  A model with
> frequency-dependent RLGC parameters, however, dissipates additional
> signal energy at higher frequencies.  As a result, certain segment
> length restrictions get relaxed as compared to the frequency-independent
> case, which is the limiting case.

Hi Steve:

Thank you for your comments.

Each segment parameter (e.g. R_segment, L_segment, C_segment, G_segment)
can be calculated by dividing the total value ( for that parameter)  by the
number of segments.

For example,  calculating L_segment involves:

L_total =  Zo * TD

Where, L_total is the total line inductance, Zo is characteristic impedance
and TD is signal propagation time delay
 [e.g. TD =  (Line Length ) / ( propagation velocity) ]

and

L_segment = L_total / (Number of segments)

Similarly, the total line capacitance is :

C_total = TD / Zo

and

C_segment = C_total / (Number of segments)

Above expressions indicate that frequency dependence of L_segment and
C_segment are governed by frequency variations of TD and Zo.

Of course, modeling a lossy requires calculating R_segment and G_segment
in addition to L_segment and C_segment.

Best Regards,

Abe Riazi
ServerWorks







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