Visjnoe wrote on Jun 6th, 2008, 12:01pm:Dear all,
assume a ring oscillator with a square wave like output and frequency fo. If one wants to calculate the RMS jitter of this oscillator,
one should integrate the phase noise, take the square root and divide by 2*pi*fo.
Which rms jitter is of interest to you?
a) absolute jitter? This is infinite for a free running oscillator.
b) period jitter?
Your method does not yield b), I'm afraid. There are two common definitions for phase noise. If you take the normalized ratio of the power spectrum of the noisy waveform over that of the noiseless waveform, total area under the curve is 1. If you take the power spectral density of the phase deviation (in radian^2/Hz), the total area is infinite. Your circuit simulator does not report rms period jitter?