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Can anyone explain what is meant by "Omega suppression" in lock-in amplifier discussions or specifications. I'm usually very good at web-searching, but have been unable to find anything that explains rather than mentions this term. I find it mentioned in some manuals but never explained.

Omega and 2 Omega sound like fundamental and 2nd harmonic, but ...?

Some mentions:

In passing only here Setting up a Digitally Tunable Resonator using the HF2LI

Many mentions here MFLI User Manual but meaning uncertain from context.

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  • $\begingroup$ Have you asked Zurich Instruments? $\endgroup$ May 3 at 14:30
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Looking at this page, the part where they explain "Signal Dynamics and Demodulation Bandwidth" (search for suppress), they give an example of AM demodulation by comparing simple filtering with a locked-in filter. In the text, they say:

For the second set of requirements, frequency components corresponding to the sidebands are rejected by reducing the filter bandwidth to a value smaller than fm [...]

I don't know whether this is what "omega suppression" is about, but it seems to fit the description. What's more, the link you give is for the same datasheet as theirs (newer, to be expected). So my guess is the device has an option for suppressing the sidebands, as described on page 59 on their datasheet (the newer one):

  • Multi-harmonic mode (optional, simultaneous measurement up to four harmonicfrequencies)
  • Arbitrary frequency mode (optional, simultaneous measurement at 4 arbitrary frequencies

I didn't read everything, just glanced, so based on these, this is my conclusion. Maybe there are others.

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