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Measurements >> Other Measurements >> simualting for sigma delta noise folding due to charge pump nonlinearity
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Message started by yvkrishna on Dec 27^th, 2013, 10:18am

Title: simualting for sigma delta noise folding due to charge pump nonlinearity
Post by yvkrishna on Dec 27^th, 2013, 10:18am

Hi,

In the context of fractional plls, the nonlinearity in the PFD+CP transfer characteristic would result in noise folding which would increase the low freq phase noise.

I want to create a simple setup to capture in spectre simulations using
1.) quantisation noise by using zvcvs ( just by plugging coefficents of NTF of sigma delta modulator(z domain TF))
2.) vcvs to create the nonlinear transfer char using pwl vector/data file (curve obtained from stand alone chargepump simulation charge Vs. delta phi (input phase difference))

If i cascade these two sources 1,2 can I really capture the folding effects(intermodulation )?
but what simualtion (ac/tran/pac ) is needed for this kind of situation?

Ofcourse modeling modulator/chargepump in timedomain or using matlab for the same is fullblown exercise to capture it completely.

Thanks,
yvkrishna