MT-008

PHASE

DETECTOR

CHARGE

PUMP

LOOP

FILTER

BPF

ADC

SAMPLING

CLOCK

NOISY

CLOCK

VCXO

DIVIDER

ADF4001, OR ADF41xx-SERIES

Figure 8: Using a Phase-Locked Loop (PLL) and Bandpass

Filter to Condition a Noisy Clock Source

The effect of enclosing a free-running VCO within a PLL is shown in Figure 9. Notice that the

"close-in" phase noise is reduced significantly by the action of the PLL.

Figure 9: Phase Noise for a Free-Running VCO and a PLL-Connected VCO

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