Dear Lawrence, [quote userid="117246" url="~/cadence_technology_forums/f/rf-design/47278/usage-of-pn-after-transient-noise-simulation"][/quote] The PN() function is used to calculate the phase noise after transient simulation with this equation: (p.55) If you read on page 56 of the first document you quoted, the expression you are showing is not the phase noise. As stated on page 56: " Transient noise output waveform is stored as vt_tran variable. Absolute jitter time-domain waveform Ja_time and its power spectrum Ja_tran is calculated using the abs_jitter() and PN() functions, respectively. " The expression for ja_tran is the power spectrum - which differs from the phase noise. Does this help at all? Shawn
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