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Measurements >> Phase Noise and Jitter Measurements >> JEE not matching with Pnoise Time-domain (strobed) analysis
https://designers-guide.org/forum/YaBB.pl?num=1319043058

Message started by rajkumar palwai on Oct 19^th, 2011, 9:50am

Title: JEE not matching with Pnoise Time-domain (strobed) analysis
Post by rajkumar palwai on Oct 19^th, 2011, 9:50am

Hi all,
For driven circuits like dividers, we see JEE as the jitter metric. In spectre Pnoise analysis we can see the JEE directly using the "Jitter" analysis. Ideally this number should be equal to the (total sampled rms noise voltage/ (dv/dt)). I have calculated the total sampled noise using the Pnoise "Time-domain' (also referred as strobed noise analysis) and then tried to match the number with the JEE number. But they are not coming out same.

Please suggest me if am doing anything wrong in the calculations.

Regards
rajkumar

Title: Re: JEE not matching with Pnoise Time-domain (strobed) analysis
Post by msr on Mar 25^th, 2012, 12:33am

Hi,

1) Formulae Jee = Vn-rms-dsb / (dv/dt at threshold crossing)

2) Vn-rms-dsb :
Spectre takes Noise BW = (Maximum Sidebands + 0.5) * F-clk. Vn-rms-dsb = SQRT( (Maximum Sidebands + 0.5) * F-clk ) * PSD-dsb
For example PSD-dsb = SQRT(4KTR) for a resistor.

But if the circuit band-width is less than the noise bandwidth then circuit bandwidth should be considered in Vn-rms calculations.

3) Calculate dv/dt in a very small voltage range around threshold at output.

Thanks
Srinivas