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Measurements >> Phase Noise and Jitter Measurements >> Jitter Measurement vs Simulation
https://designers-guide.org/forum/YaBB.pl?num=1108585435

Message started by ic_engr on Feb 16^th, 2005, 12:23pm

Title: Jitter Measurement vs Simulation
Post by ic_engr on Feb 16^th, 2005, 12:23pm

Hello Everyone,

I was trying to design an oscillator with a known jitter. I also had an existing oscillator in 0.18um technology. The measured jitter in TIE of 30us was 1.4nsec. The period jitter was 483psec. The oscillator frequency is 4MHz.

I used tdnoise in Spectre to predict the jitter for the oscillator for which I have measured results. When I integrated the noise on the tdnoise form from 33.3kHz to 2MHz (fo/2) as in Ken's paper, I got 10.4mV. I divided this number by the SR of the ring oscilltor (6.5MV/sec) and I got 1.6nsec. This is pretty close to what I have on silicon (1.4nsec measured). DId I do anything stupid here!.

Can anyone tell me if I did the right thing by intergating from 33.3kHz to 2MHz. If I integrate from a lower frequency (1kHz to 2MHz) I see the jitter is prety large due to 1/f contributions. the fc is at 10kHz.

Using the same strategy I predicted the jitter for my new oscillator and it seems to be about 14pSec when integrating 33kHz to 2MHz.

I thuought I should have multiplied by sqrt(fo*30us) for k-cycles jitter. Did I already take care of it by doing integration from 33kHz to 2MHz.

Does the multiplication factor for k-cycles jitter only comes in when tdnoise is integrated at higher frequencies.
I set the sweep in pnoise for tdnoise to absolte.

Any suggestions will be appreciated.

ic_engr

Title: Re: Jitter Measurement vs Simulation
Post by Tommy on Feb 17^th, 2005, 8:53pm

Iam no expert in this. But if I have followed my math correctly, that integration gives a 1-sigma value of Phase jitter.

I think a better approach to simulate jitter would be to use voltage-domain behavioural model of the oscillator & dither its timing events (The dithering value should be calibrated from the circuit as described by Ken in the Jitter paper). You could dump the threshold crossing times of the oscillator to a file & use the formulas to compute whatever jitter metric you want to compute by writing an appropriate Matlab script (or a C program).

Thanks
Tommy

Title: Re: Jitter Measurement vs Simulation
Post by ywguo on Apr 5^th, 2005, 8:02pm

Hi,

Can you explain the measured jitter in TIE, period jitter, and phase jitter for me and their relationship? It has many definitions for jitter. Sometimes I am confused.

I will appreciate very much.

Yawei