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Phase noise simulation in ring oscillator

Ayrin

I have two questions regarding the phase noise simulation results (PSS + Pnoise) for ring oscillators:

(1) How much the precision of the initial oscillation frequency is important in estimating phase noise ?

(2) The results that I get for the phase noise seems a bit high. I feel there is a shift up in all the frequencies. In very low frequencies (close to carrier) the phase noise is largely positive. Comparing with the analysis presented in [Abidi, JSSC 2006] the phase noise sounds very high. Does someone has any idea that what could be wrong?

 

The ring oscillator designed to oscillate at 2.4 GHz using CML gates with a tail bias current of about 200 uA. 

 

Thanks in advance for your help.

 

Armin

 

Parents
  • Hi Andrew,

    > There are a number of things which are incorrect in your reply, Shawn

    Thank you for your corrections Andrew. I was providing my thoughts based on my many experiences over the years with PSS/pnoise to generate repeatable and accurate results. I must apologize for any of comments that are not accurate - I do not want to mislead anyone!

    With respect to the impact of TSTAB, I documented a series of PSS/pnoise simulations were I varied TSTAB and observed differences in the resulting PSS and pnoise solutions. In this example, the design was an LC oscillator and the shooting method was used. Of course, I fully realize the the PSS algorithm has changed over the years, and perhaps the most recent algorithm is less dependent on TSTAB. Perhaps this is responsible for the dependence I observed.

    Thank you for your discussion of the defaults for maxstep. I was aware of its being set indirectly by parameters such as errpreset and the highest harmonic. The reason I made mention of it was I found that many users do not set errpreset or the number of harmonics to generate accurate results. I often recommend that, in lieu of setting these indirect parameters, the consider setting maxstep to a minimum of about 20 to 100 points per period depending on oscillator Q. In this fashion, even if the user does not set the number of harmonics, for example, to an appropriate value, at least the integration algorithm uses a minimum number of points per waveform. I hope you do not consider this misleading...

    Thank you for your insights (again),

    Shawn
Reply
  • Hi Andrew,

    > There are a number of things which are incorrect in your reply, Shawn

    Thank you for your corrections Andrew. I was providing my thoughts based on my many experiences over the years with PSS/pnoise to generate repeatable and accurate results. I must apologize for any of comments that are not accurate - I do not want to mislead anyone!

    With respect to the impact of TSTAB, I documented a series of PSS/pnoise simulations were I varied TSTAB and observed differences in the resulting PSS and pnoise solutions. In this example, the design was an LC oscillator and the shooting method was used. Of course, I fully realize the the PSS algorithm has changed over the years, and perhaps the most recent algorithm is less dependent on TSTAB. Perhaps this is responsible for the dependence I observed.

    Thank you for your discussion of the defaults for maxstep. I was aware of its being set indirectly by parameters such as errpreset and the highest harmonic. The reason I made mention of it was I found that many users do not set errpreset or the number of harmonics to generate accurate results. I often recommend that, in lieu of setting these indirect parameters, the consider setting maxstep to a minimum of about 20 to 100 points per period depending on oscillator Q. In this fashion, even if the user does not set the number of harmonics, for example, to an appropriate value, at least the integration algorithm uses a minimum number of points per waveform. I hope you do not consider this misleading...

    Thank you for your insights (again),

    Shawn
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