SNAA393 January   2024 LMK6C , LMK6D , LMK6H , LMK6P

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
    1. 1.1 Why use a Phase Noise Analyzer?
  5. 2Understanding Phase Noise Plots
  6. 3Phase Noise Analyzer Measurement Settings
    1. 3.1 Start or Stop Frequency
    2. 3.2 Averaging and Correlation
    3. 3.3 Persistence
    4. 3.4 Spurious View Modes
    5. 3.5 Other Settings
  7. 4Hardware Setup for Different Clocking Formats
    1. 4.1 LVCMOS
    2. 4.2 LVDS
    3. 4.3 LVPECL/HCSL
    4. 4.4 Balun Recommendations
  8. 5Typical Measurements with Different Termination Schemes
    1. 5.1 LVCMOS
    2. 5.2 LVDS
    3. 5.3 LVPECL
    4. 5.4 HCSL
  9. 6Summary
  10. 7References

Averaging and Correlation

To reduce uncertainty from a single measurement point, averaging can be used. Averaging over several measurements smooths out the phase noise trace to give a more realistic phase noise measurement at any given frequency offset. When averaging is enabled, cross correlation can also be adjusted. Correlation measures the input signal against different reference sources. Since the noise profiles of the different reference sources are correlated, the reference noise is subtracted out and the resulting measurement is a better representation of the signal rather than noise from the measurement equipment. Increasing the correlation is especially important when measuring the noise floor of a very clean clock source.