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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

  • Hi Andrew,

    I also have been stuck with the problem of selecting the proper fmin in long term ( accumulated ) jitter calculation in PSS/PNOISE sims. I would like to get some more clarification on the last statement "The lower limit of 1kHz is OK, but in practice if K is 1000 you are only including frequencies as low as 10MHz/1000 - i.e. 10kHz. The integration automatically takes this into account - so it's fine to leave it as 1kHz."
    Does spectre Jc(K) form always takes Fmin as "Fbeat / K" for integration, irrespective of what fmin value we give ..? Could you kindly point me to the theoretical basis for this "Fbeat / K"...? ( I am asking this because I have not found any literature which clearly specifies the Fmin of integration for K cycle accumulated long term jitter)

    Following is my specific scenario.:
    I have an experimental/simple RC relaxation oscillator operating at 10MHz. Ran PSS/PNOSE with Fbeat=10MHz. Want to find out the accumulated jitter for 100000 cycles.
    In the Jc(K) form, max integration range is set to =Fbeat/2 = 5MHz. I tried different fmin ( like 10Hz ,50Hz , 100Hz ). Follwing are the respective jitter values reported by spectre ==> 431nS , 132nS , 56nS. ==> The values are vastly different. Kindly let me know your thoughts/advice on this as this is inconsistent with the comment you have given.
    I am concerned about what value I should give as Fmin... ? Wondering if I am getting this issue due to some setting or version issue ? ( I use Virtuoso 6.1.6-64b )
    ( Based on your comment, the Fmin in my case should have to be 10MHz/100000 = 100 and Jc(K=100000) values should have to be same if I input Fmin=100Hz or 50Hz or 10Hz )

    Highly appreciate your help...

    Thanks and regards
    Soman

Reply

  • Hi Andrew,

    I also have been stuck with the problem of selecting the proper fmin in long term ( accumulated ) jitter calculation in PSS/PNOISE sims. I would like to get some more clarification on the last statement "The lower limit of 1kHz is OK, but in practice if K is 1000 you are only including frequencies as low as 10MHz/1000 - i.e. 10kHz. The integration automatically takes this into account - so it's fine to leave it as 1kHz."
    Does spectre Jc(K) form always takes Fmin as "Fbeat / K" for integration, irrespective of what fmin value we give ..? Could you kindly point me to the theoretical basis for this "Fbeat / K"...? ( I am asking this because I have not found any literature which clearly specifies the Fmin of integration for K cycle accumulated long term jitter)

    Following is my specific scenario.:
    I have an experimental/simple RC relaxation oscillator operating at 10MHz. Ran PSS/PNOSE with Fbeat=10MHz. Want to find out the accumulated jitter for 100000 cycles.
    In the Jc(K) form, max integration range is set to =Fbeat/2 = 5MHz. I tried different fmin ( like 10Hz ,50Hz , 100Hz ). Follwing are the respective jitter values reported by spectre ==> 431nS , 132nS , 56nS. ==> The values are vastly different. Kindly let me know your thoughts/advice on this as this is inconsistent with the comment you have given.
    I am concerned about what value I should give as Fmin... ? Wondering if I am getting this issue due to some setting or version issue ? ( I use Virtuoso 6.1.6-64b )
    ( Based on your comment, the Fmin in my case should have to be 10MHz/100000 = 100 and Jc(K=100000) values should have to be same if I input Fmin=100Hz or 50Hz or 10Hz )

    Highly appreciate your help...

    Thanks and regards
    Soman

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