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LMX2594: floor noise

KOUICHI NAKAJIMA
Prodigy 20 points
Part Number: LMX2594
Other Parts Discussed in Thread: LMX2820

Tool/software:

Hello,

Am I correct in assuming that the floor noise of the LMX2594 (or LMX2820) is at thermal noise level (≈ -174 dBm/Hz)?

Floor noise is where you are far enough away from the carrier.
For example, 20 MHz and 100 MHz offsets.(Where not affected by VCO noise or loop filters.)

Does the use of a divider in the LMX2594 (or LMX2820) change the noise floor?

We want to calculate the noise when the start is an oscillator, just as we calculate the NF of a receiver circuit.

Regards,


koichi Nakajima

  • 0
    TI__Guru* 97080 points

    HI Nakajima-san,

    Synthesizer is an "active" device, the noise floor is not equal to thermal noise. 

    The output divider and the output buffer of a synthesizer determines the overall noise floor. 

  • 0 in reply to Noel Fung
    Prodigy 20 points

    Thank you.

    The description was found in the data sheet.
    'Figure 21. additive VCO Divider Noise Floor' and 'Figure 6-3. Noise Floor'.