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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,

     

    Coming back to the issue of phase noise simulation for a ring oscillator, I have seen again the two following issues:

    (1) for a differential ring oscillator, the simulated phase noise at 1 MHz offset is just very high (about 0 dBC/sq.Hz). I don't think this is correct. Here I introduce /voutp and /voutn as the outputs of the oscillator in the pnoise simulation table.

    (2) when I redo the simulation and  introduce the outputs in the pnoise simulation table as: /voutp and /gnd!, then the simulated phase noise goes done by about 100 dB ! Now this one sounds to me like a very good number, much better than the expected !

     

    Do you have any suggestion for a reliable simulations ?

     

    Thanks,

     

    A.

Reply

  • Hi,

     

    Coming back to the issue of phase noise simulation for a ring oscillator, I have seen again the two following issues:

    (1) for a differential ring oscillator, the simulated phase noise at 1 MHz offset is just very high (about 0 dBC/sq.Hz). I don't think this is correct. Here I introduce /voutp and /voutn as the outputs of the oscillator in the pnoise simulation table.

    (2) when I redo the simulation and  introduce the outputs in the pnoise simulation table as: /voutp and /gnd!, then the simulated phase noise goes done by about 100 dB ! Now this one sounds to me like a very good number, much better than the expected !

     

    Do you have any suggestion for a reliable simulations ?

     

    Thanks,

     

    A.

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