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Jan Hovius · Guest

My subject in fact says it all:

We want to plot the fundamental frequency vs. the tuning voltage of a
VCO during a swept PSS analysis run but up until now all we end up
with is that it only shows the fundamental belonging to one (the
latest) tuning voltage.
There is a more complex workaround: A parametric transient run (in
which also the Vtune is swept) and extracting the frequency of the
resulting transient (via the "frequency" function in the calculator)
but we wonder whether it is possible defining a swept PSS .

Andrew Beckett · Guest

Hi Jan,

Use Results->Direct Plot->Main Form, and then on the pss page, pick
Harmonic Frequency and choose 1 in the list box below. It should show the range
of the frequency over the sweep. I just did this with a VCO and swept the
control voltage, and I got a plot of frequency versus contrl voltage.

This works whether you do it via parametric analysis, or using the sweep on the
pss form itself.

You can also use the "Add to Outputs" on the direct plot form to figure out what
calculator expression to use to get this information.

The alternative is to do a transient analysis, sweeping the control voltage
(slowly), and then using the freq_meter component from analogLib which measures
instantaneous frequency.

Regards,

Andrew.

--
Andrew Beckett
Senior Technical Leader
Custom IC Solutions
Cadence Design Systems Ltd

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