Dear Sir/Madam

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

Thanks.

Dear Sir/Madam

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

Thanks.

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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:

- Increase the PFD frequency, or
- Decrease the loop bandwidth.

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: