I understand that you are observing a mismatch between the phase noise set using the ‘VCO impairment’ block and the phase noise measured using the ‘Phase Noise Measurement’ block in Simulink. Here are a few reasons due to which this might be happening:
- The ‘Phase Noise Measurement’ block measures phase noise by analysing the ‘Power Spectral Density’ (PSD) of the phase deviation from a reference carrier. Since this is a statistical quantity, short simulation times might lead to noise PSD estimates.
- The measurement resolution, which can be set by the ‘Resolution bandwidth’ parameter of the block, might be coarse/ not adjusted to match the exact noise profile.
- The phase noise block adds impairment, but if the noise is measured after other blocks (e.g., modulators), the nonlinearities added by these blocks might distort results.
You can try modifying the parameters mentioned above to get a more accurate estimate of the noise in the system. Please refer to the following documentation links for more information about the ‘Phase Noise Measurement’ and ‘VCO’ blocks: https://www.mathworks.com/help/releases/r2025a/msblks/ref/phasenoisemeasurement.html
I hope this helps.
