[SI-LIST] Re: [SI-LIST]: Which tool is the best - LINPARdiscussion
- From: Raymond Anderson <Raymond.Anderson@xxxxxxx>
- To: "'si-list@xxxxxxxxxxxxx'" <si-list@xxxxxxxxxxxxx>
- Date: Thu, 22 Apr 2004 10:15:26 -0700
Raj Raghuram wrote:
>>I am not sure modeling with S-params would work for long transmission
>>lines i.e. metres in length. Most s-parameter simulators use a rational
>>fit which in the end is a lumped model. Maybe you can comment on this.
>>
>>
The delay information required to model an electrically long structure
such as a transmission line is contained in the phase information of the
complex s-parameters.
Most instruments output the phase of s-parameters in the range of +180
to -180 degrees. Plotted wrt frequency it resembles a sawtooth. This
modulo 360 phase info needs to be unwrapped into a linear phase
progression to interpret it as delay.
When a rational polynomial approximation is fitted to the unwrapped
s-parameter data, if the phase part of the approximation is the same as
the phase of the original s-parameter then I'd expect the resultant
macromodel to exhibit the same delay characteristics.
Comments ???
-Ray Anderson
Sun Microsystems Inc.
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