ussmueller
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Dear all,
I'm currently trying to implement a DeltaSigma (DS) modulator phase domain model. I have not understood the model in Ken's paper (Predicting the phasenoise and jitter of of PLL based frequency synthesizers, page 24).
parameter real n = 0 from [0:inf); // white output phase noise (rads2/Hz) parameter real bw = 1 from (0:inf); // ΔΣ modulator bandwidth parameter real fmax = 10∗bw from (bw:inf); // maximum frequency of concern ... Theta(out) <+ Theta(in) / (ratio + noise_table([ 0, n, bw, n, fmax, n∗pow((fmax/bw),order) ], “dsn”));
The divide ratio consists of the "wanted" part ratio and the deltasigma noise. Ratio can be a fractional number. The delta sigma noise is modeled with the noise_table function. The noise of the divider is not modeled. Are these assumptions corrrect?
What do the parameters n, bw and fmax describe? Is fmax = fref/2? What is meant by DS bandwidth. To my understanding a DS has a constant slope of order*20dB/dec and has no high pass function. How to extract the parameter n?
Is it possible to use a transfer function in the zdomain (e.g. (1  z^1)^3 for a MASH111) instead of the noise_table function?
Thanks for your support. Thomas
