Andrew Beckett
Senior Fellow
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Life, don't talk to me about Life...
Posts: 1742
Bracknell, UK
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One way to see this is to use the "Add to Outputs" button on the Direct Plot form - this will send the expression to the ADE outputs, and then if you double click on it you can see the expression.
If it's a recent version (IC615 ISR12 onwards), then the expression will be something like pn('pnoise). As part of the effort to simplify RF expressions, a lot of the underlying functions have been wrapped to make them shorter. The pn function calls the phaseNoise function underneath, and the phaseNoise function takes (at least) two arguments - the harmonic number and the name of the large signal result database. Typically it would be something like phaseNoise(1 "pss_fd" ?result "pnoise") - the ?result bit says the database containing the noise results. So this means use the magnitude of the signal specified as the pnoise output at the 1st harmonic in the large signal result as the carrier magnitude to normalize the output noise to.
If using pn('pnoise), what it does is use the recorded relative harmonic number (or vector) - this is what you specified when setting up the pnoise. If however you specified an absolute sweep, then it always uses 1 as the first argument to the phaseNoise function.
If using IC5141 or an older IC61 version prior to this expression simplification work, then the direct plot form will also generate the phaseNoise expression using the same logic as described above.
So, to get what you want, you'd need to directly use the phaseNoise function (e.g. in the calculator, or add it in the ADE outputs pane) with whatever harmonic number you want as the first argument.
Hope that helps!
Regards,
Andrew.
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