L M X 2 5 3 1 L Q 2 8 2 0 E E V A L U A T I O N B O A R D O P E R A T I N G I N S T R U C T I O N S
Far-out Phase noise is worse than evaluation board instructions
show
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Ensure the measurement equipment noise floor is not limiting the measurement. For
spectrum analyzers, the noise floor at a particular setting can be measured by removing the
RF input signal
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If the settings are changed from what the board was designed for, ensure the delta-sigma
modulator is not increasing the far-out noise. To determine this, tune to an integer channel
and set the ORDER bit to “Reset Modulator”. The far out phase noise should not decrease. If
it does, try a loop filter with more attenuation or select a lower order delta-sigma modulator.
Device Data
The next few pages show data collected from the LMX2531LQ2820 evaluation board.
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