Analog Devices ADRV9005 Reference Manual page 113

Reference Manual
SYNTHESIZER CONFIGURATION AND LO OPERATION
When changing the loop filter bandwidth, the typical consideration is the wider the bandwidth, the better the close-in band noise, but the worse
the far-out band noise. Trade off between the two to find the optimal setting for the specific application. Note the highest phase frequency
detector (PFD) frequency the ADRV9001 supports is 307.2MHz.
Figure 101 shows that the PLL phase noise is highly dependent on the PFD frequency (REF_CLK). A higher PFD frequency achieves a better
phase noise.
Figure 102 shows where a trade off can be made between the close-in phase noise and far-end phase noise by adjusting the loop filter
bandwidth. As mentioned, the higher the loop filter bandwidth, the better the close-in noise but with the scarification of the far-end noise, and
vice versa.
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Figure 100. PLL Phase Noise Contributors
Figure 101. Effect of PFD (REF_CLK) Frequency on PLL Phase Noise
ADRV9001
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