[SI-LIST] Re: [SI-LIST]: Which tool is the best - LINPARdiscussion
- From: Raj Raghuram <raj.raghuram@xxxxxxxxxxxxxxx>
- To: Raymond.Anderson@xxxxxxx
- Date: Thu, 22 Apr 2004 16:49:38 -0700
Ray,
Yes, it would be easier to interpret the phase data as a delay if the
pahse varied uniformly over the frequency range. I would imagine that a
good s-parameter simulation program would interpret the phase
information correctly whether it is in the sawtooth form or as varying
linearly over the frequency range of the data. If the program deals with
the s-parameter data in the real-imaginary form rather than the
magnitude-phase form, it should not matter.
I was worried about the issue of the rational fit. With a large delay,
it puts a greater burden on the fitting program. The same structure
simulated as a transmission line can have the delay extracted out.
Raymond Anderson wrote:
>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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--
Raj Raghuram
Berkeley Design Automation (http://berkeley-da.com)
2902 Stender Way,
Santa Clara, CA-95054
PH: (408)-496-6600 ext.203
Cell: (408)-390-7614
EMAIL: raj.raghuram@xxxxxxxxxxxxxxx
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