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pnoise simulation of DLL

ycyeh

Hi,
I am now working on the delay locked loop simulation. I use a circuit level design for the voltage-controlled delay line, and verilog-a model for the phase detector and charge pump. My target is to simulate the in-band pnase noise (jitter) coming from the delay line will be suppressed compared with open-loop case(not including any noise from phase detector and charge pump). However, this is only observed while I choose the noise type to source, but not the same effect if I choose jitter as the noise type and plot the jee spectrum. Is there any one having the experience on these kind of simulation? I saw that jitter simulation is recommended especially for measuring the jitter for square wave. On the other hand, there are many documents talking about integrate the phase noise to get the jitter. Should the jitter caculation result from different noise type (source or jitter) be consistent to each other?

This is the link to my simulation result plot:
docs.google.com/.../edit

Thanks,

ycyeh 

  • Using the phase noise from sources to compute jitter only really makes sense for sinusoidal type outputs. The "sources" method gives you the time-averaged noise over the period, whereas in a switching circuit, you only really care about the noise at the transitions. The "jitter" mode (at least the PM jitter mode) strobes the output of the circuit at the threshold crossing you specify, and measures the noise at that instant, and this combined with the slew rate of the signal gives you the jitter. If you're using the sources mode, you're effectively including the noise over the entire period. For a sinusoidal oscillator, it's typically mostly PM noise anyway, but for other kinds of circuit you may have AM noise in there too and consequently it's not going to give you the right answer.

    The relationship between the results from sources and jitter is complex (often there isn't really a simple relationship, if at all), so trying to compare them is in most cases fruitless.

    Regards,

    Andrew.

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