Time-Domain Reflectometer Analysis (tdr)
Description
The time-domain reflectometer analysis linearizes the circuit about the DC operating point and computes the reflection coefficients versus time, looking from the active ports into the circuit.
Syntax
Name tdr parameter=value ...
Parameters
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stop
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Stop time.
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settling
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stop
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Time required for circuit to settle.
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start
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-0.1*stop
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Time output waveforms begin.
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smoothing
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2
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Window smoothing parameter (useful range is 0 to 15).
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vel
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1
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Propagation velocity of medium normalized to c.
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points
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64
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Number of time points.
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ports
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[...]
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List of active ports. If not given, all ports are used.
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readns
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File that contains estimate of DC solution (nodeset).
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useprevic
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no
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If set to yes or ns, use the converged initial condition from previous analysis as ic or ns. Possible values are no, yes and ns.
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restart
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yes
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Restart the DC solution from scratch if any condition has changed. If not, use the previous solution as initial guess. Possible values are no and yes.
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annotate
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sweep
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Degree of annotation. Possible values are no, title, sweep, status and steps.
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title
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Analysis title.
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oppoint
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no
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Should operating point information be computed; if yes, where should it be sent. Operating point information would not be output if the operating point computed in the previous analysis remains unchanged. Possible values are no, screen, logfile and rawfile.
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prevoppoint
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yes
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Use the operating point computed on the previous analysis. Possible values are no and yes.
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Such a small-signal analysis begins by linearizing the circuit about an operating point. By default, this analysis computes the operating point, if it is not yet known, or recomputes it, if any significant component or circuit parameter has changed. However, if a previous analysis computed an operating point, you can set prevoppoint=yes to avoid recomputing it. For example, if you use this command when the previous analysis was a transient analysis, the operating point is the state of the circuit on the final time point.
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