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VCO jitter calculation using PNOISE simulation

chadong

Hi all,

I have two questions about pnoise jitter calculation in SpectreRF.

1. What is the meaning of Freq. Multiplier in jitter calculator?

2. What is the optimum integration range of phase noise for jitter calculation?

Actually, I posted about similar subject last year, but I'm still confused..... : ( 

 

I need to calculate VCO's jitter to estimate the SNR limit of synchronous ADC by clock.

I've done PSS/PNOISE simulation like following condtion 

- Free running VCO

- VCO clock speed : 10MS/s

- Total ADC conversion time : 100us(1000cycle)

- PSS

Beat frequency : 10MHz

Output harmonics(Number of harmonics) : 0

- PNOISE

Output Frequency Sweep Range : 1~500MHz(I have no idea what's the right sweep range. I just think it would be wide enough)

Maximum Sideband : 40(40 is enough to get accurate results in my case)

Noise type : Jitter(Typically, ADC needs only RMS jitter, not phase noise)

 

After PSS/PNOISE simulation, I caculated k-cycle jitter because the VCO is autonomous system and I need accumulated RMS jitter.

Following is what I did.

Results->Direct Plot->Main Form->select pnoise jitter(Analysis)->Jc(Function)->Number of cycles=1000->select RMS->

->Freq. Multiplier=1->Integration Limits:1kHz~20MHz

 

Here are two questions as I asked above.

1. What is the meaning of Freq. Multiplier in jitter calculator?

2. What is the optimum integration range of phase noise for jitter calculation?

I think the integration range of 1k~20MHz is enough, because total ADC's conversion time is 100us and 20MHz=10MHz(Fundamental X2)

Is it proper approach?

Parents

  • Your comment is really helpful to understand PSS sim.

    Thank you for your reply, Andrew

     

    I read the app note you suggested(for version MMSIM6.0, March 2006), and I'm little confused about k-cycle jitter.

    From the note, section "Synchronous Jitter Versus Accumulating Jitter", autonomous circuits, e.g. VCO have only cycle-to-cycle jitter as the jitter performance as mentioned below

    "For autonomous circuits where there are no ideal reference transitions, you are limited to using self-referred jitter metrics. This jitter is accumulating jitter. The next cycle transition is the result of the previous cycle output, so the jitter variance accumulates from cycle-to-cycle"

    But, in the Figure 1-9 of the note, Cycle jitter is used as the jitter performance of VCO. 

    Could I use the K-cycle jitter as accumulating jitter of autonomous circuits?

    Which is right?

Reply

  • Your comment is really helpful to understand PSS sim.

    Thank you for your reply, Andrew

     

    I read the app note you suggested(for version MMSIM6.0, March 2006), and I'm little confused about k-cycle jitter.

    From the note, section "Synchronous Jitter Versus Accumulating Jitter", autonomous circuits, e.g. VCO have only cycle-to-cycle jitter as the jitter performance as mentioned below

    "For autonomous circuits where there are no ideal reference transitions, you are limited to using self-referred jitter metrics. This jitter is accumulating jitter. The next cycle transition is the result of the previous cycle output, so the jitter variance accumulates from cycle-to-cycle"

    But, in the Figure 1-9 of the note, Cycle jitter is used as the jitter performance of VCO. 

    Could I use the K-cycle jitter as accumulating jitter of autonomous circuits?

    Which is right?

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