smlogan
Community Member
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Posts: 52
Boston, MA
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I just provided the following response on the Cadence forum.
[i][i][i]Dear Yevgeny,
> I deem the two analyses should have given same spectra, but they don't. In fact, the base harmonic
> (i.e. number "0") is exactly identical, all the others as not.
My understanding is that a PAC analysis maps a given input frequency (in this case the power supply modulation frequency) to the various output frequencies it will produce due to amplifier. You do note that the THD of the amplifier is better than 30 dB. Howver, I assume that is the THD from the amplifier input - not from an input on the supply rail. Hence, my guess is you observe significant sidebands at the amplifier output due to the supply noise modulation frequency.
A PXF analysis maps an output harmonic back to the input frequencies that are required to generate that output harmonic. Hence, the two analyses, from my understanding, will not produce the same output spectra. PAC provides information on the output frequencies produced from a given input - and PXF provides insight on the input frequencies required to produce a given output frequency.
Let me know your thoughts, or if I misinterpreted your question![/i][/i][/i]
Shawn
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