What is meaning of SDM in the frequency domain analysis? This SDM seems contributing a lot to the phase noise. And the previous version of simPLL4.0 seems it donesn't have this SDM paratmeter
SDM noise is the Sigma Delta Modulator noise. It only appears on fractional-N PLLs (the SDM is what does the fractional division). I'm guessing in your previous simulation, you were using an integer-N PLL. ADIsimPLL v4.0 has SDM noise.
The SDM noise peaks at half the PFD frequency. If you increase the loop bandwidth, you'll see this. To reduce the noise, either:
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