Baseband Noise Measurement for DC control source for VCO

Measurement Setup

  1. Press Meas/View > Baseband Noise to select the Baseband noise measurement window. Press Window Max to maximize the window.  

  2. Press Trigger > Trigger to Baseband Noise > Continuous to start measurements.

  3. Press Trigger > Source > Internal.

  4. Connect the DC source (for a VCO Vtune) to the “BASEBAND IN” port with a BNC cable. Set the DC voltage to a control voltage value (12 V etc.) for the VCO.

  5. Press Start/Center (Stop/Span), set Start > 1Hz and Stop > 40MHz.

  6. Press Setup > IF Gain > 50 dB.  When "IF A/D overflow" is displayed, decrease 10 dB from the current IF Gain setting (Press Setup > IF Gain).

  7. Press Avg/BW > Avg factor > 5, and Averaging > ON to reduce fluctuation, then press Averaging Restart.

  8. Press Scale > Auto Scale.

Analysis

Phase Noise vs Baseband Noise

  1. Connect the DC source to the VCO (Vtune) and connect the output of the VCO to the “RF IN” port of the E5052B.

  2. Press Meas/View > Show Window > Layout Window > Two Windows and then press the following screen layout.

  3. Press Meas/View > Show Window > Spectrum Monitor to toggle OFF, and press Freq & Power to toggle OFF, Transient to toggle OFF, AM Noise to toggle OFF.

  4. Press Window Max to display two measurement windows (Phase Noise and Baseband Noise) on the screen.

  5. Press Meas/View > Phase Noise to select the phase noise measurement window.

  6. Press Trigger > Trigger to Phase Noise > Continuous to start measurements.

  7. Press Trigger > Source > Internal.

  8. Press Setup > Capture Range > Normal for PLL method.

  9. Press Setup > Auto Setting.  When "IF A/D overflow" is displayed, please try to decrease 10 dB from the current IF Gain setting (Press Setup > IF Gain).

  10. Press Start/Center (Stop/Span), set Start > 100Hz and Stop > 40MHz.

  11. Press Avg/BW > Avg factor > 5, and  Averaging > ON to reduce fluctuation, then press Averaging Restart

  12. Press Scale > Auto Scale

The phase noise of the VCO is highly affected by the noise itself from the DC source.

When a commercial DC source is used, the phase noise of the VCO controlled by the commercial DC source may not be properly measured.

When the DC control of the E5052B is used for the VCO, it enables the very accurate phase noise measurement for the VCO.

The data traces for the phase noise measurement window and baseband noise measurement window are the measurement results when the built-in DC control of the E5052B is used.

 

More Information

For more information about Baseband Noise Measurement, see Baseband Noise Measurement.