Hi all,
        I am a bit confused about what formula does the cadence calculator uses in it's inbuilt skill function for period jitter.

Acc. to me,
                If periods(1:1000) denotes 1000 samples of Time Periods of a jittery waveform measured over 1000 cycles, then

jitter_zeromean = periods - mean(periods);
Single_period_jitter = sqrt ( mean ( jitter_zeromean .^2 ) );

But, this formula shows different results than cadence's inbuilt period jitter skill.

Can somebody pls explain the formula used by this skill OR if something'swrong in my formula to calculate period jitter ??.

Also, for adjacent cycle period jitter, what should be the bin size in this function ??

--
mayank.

Hello Andrew,
                     I tried matching my results from matlab post-processing to cadence calculator's period jitter skill...

   i found out that period jitter skill in cadence calculator uses the same formula Quote:

but the mean is a moving window average whose window size is equal to binsize...

i.e. if    T1, T2, T3,... denote consecutive periods of the waveform, & random variable X denotes period jitter,
  then   X1 = T2 - (T1+T2)/2; X2 = T3 - (T2+T3)/2; X3 = T4 - (T4+T3)/2 and so on....

Am i correct ??

--
Mayank.

Thank you Sir,
                    That explains it all...  
    & yeah 1 more question.....If we do PLL Macro Model Simulation, And use Direct Plot Form's Plot PLL Noise PSD, It generates a PLL Phase Noise plot, but it also indicates a value of center frequency & Jitter alongside.
  What Jitter metric is this ??
---->  Single Period Jitter calculated from time domain waveform of PLL o/p which goes to freq. meter (with bin size 2)  ??
---->  Or is it calculated from frequency domain phase noise plot that PLL PSD option generates ??
If it is calculated from frequency domain, which conversion formula does it use ?? -- Zanchi / Demir / Frank Wiedmann's / Allan Variance / or other ??

thanx,
Mayank.