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Jitter cacluation from phase noise??

chadong

Hello everyone,

Maybe many RF & IC designers must be suffer from jitter calculation from phase noise like me.

I read almost all the major documents in google(e.g. Jitter measurements using SpectreRF Application note)

However I can't find any explicit answer or solution about jitter calculation.

Can anybody help me understand the jitter calculation?

My question is simple.

How can I decide the phase noise integration range to calculate jitter?(with selecting noise type as jitter in pnoise)

In many papers, the range was selected 1kHz(10kHz)~10MHz. What's the reason?

In ADI's application note(for ADC), the range was selected 100~2*Fout(i.e. twice of sampling frequency)

Although there are many documents about it, I'm still confused.

Why the phase noise in high frequency is not integrated??

How can I select the low-frequency limit and high-frequency limit for RMS jitter calculation? 

 

Followings are other questions

1) in PSS simulation

-Output harmonics:Number of harmonics

If I am right, the number of harmonics means how many harmonics will be consisted in PSS analysis.

When smaller number used, more noise folded into low frequency. right?? If I'm wrong please point out.

2) in PNOISE simulation

-Output Frequency sweep range

I can't understand this parameter. Even in spectreRF manual, there's no explanation about this.

If I make a free running oscillator 100MHz, what frequency has to be stop frequency? 50MHz? 200MHz?

I selected start frequency to 1Hz

-Sidebands

Maximum sidebands determines the noise folding range

If one sets it 7, noise at higher frequency than 7th sideband will be folded into 1~7 sidebands. right?

 

Thank you for reading

  • Ok, this confirms my assumptions. Noisetype sources will give you unsampled noise, noisetype jitter (PM jitter, anyway) will give you sampled noise. For sampled noise, you only need to sweep up to 40 MHz (half the "beat frequency", see my reply from 05-13-2011).

    I have already recommended you to use PM jitter in an earlier reply. I have never used FM jitter, I do not know how it works exactly and how much I can trust the results. I have worked quite extensively with PM jitter and have always got good results so far.

  • Thanks again for your patience. The for which I use FM instead of PM, is based on a White Paper from Caden, by Ken called:"Modeling and Simulation of Jitter in PLL Frequency Synthesizers. On page 3, table 1 refers VCO's to be simulated as FM and driven systems as PM.

    Regarding the sweep, I thought that fo/2 was only used for the integration limits of jitter.Thanks for this piece of information.

    Relating to my simulation, if I calculate between 1 and fo/2, the jitter changes quite a lot because it starts to have the influence of the first harmonic. On the other hand I am not confident to integrate, let's say till 10 MHz because the result doesn't change at all. Integrating till 100k , 1M, 10M is the same thing. The only variation appears between 30M and 40M. My question is: am I double counting the noise if I integrate till fo/2 ?

     Thanks a lot.

    Pedro

  • You should always integrate sampled noise from zero to half of the "beat frequency". Any other integration limits do not make much sense from my point of view because of the noise folding in the simulation results for sampled noise (see figure 3 and also the sentences at the bottom of page 6 and at the top of page 8 of http://www.designers-guide.org/Analysis/sc-filters.pdf). You should also make sure that you have chosen the correct value for the maxsideband parameter (see section 2.2.1 of http://www.designers-guide.org/Analysis/sc-filters.pdf).

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