How can you measure IMD using LabView 7.1?

[rsv]

Is there any way to measure IMD using LabView 7.1?

[Bob_Y.]

I assume that you mean InterModulation Distortion? IMD is the measurement of the first pair of unwanted sidebands compared to the desired ones. You can take the spectrum of the signal and from it get the measurements of the sidebands. I haven't done this but it should be fairly straight-forward.

There is also 'SVT Intermodulation Distortion.vi' in the sound and vibration toolkit.

Hope that this helps,
Bob

[rsv]

So is the IMD just the ratio of the sidebands to the desired signal, or are there some other formulas I need to use?

[Bob_Y.]

I think it depends on what you are looking for. Try looking at this app note from Anritsu or this one from Maury Microwave.

Basically, intermodulation distortion is where two signals mix and create undesired sidebands. If you have a desired signal at 6K and a second desired signal at 10K you will get some distortion at 4K (10-6) and at 16K (10+6) as well as the possibility of out of phase distortion at 4 (6-10 = -4). I believe IMD is a ratio of the sum of the distortions to the original signals. Sometimes IMD is measured as a particular order of distortion (just a single defined sideband).

I am sorry that I am not answering this very well, but it has been years since I did any of this sort of thing and I don't want to give misleading information based on half remembered facts. Perhaps if we had more information . . .

Hope that this helps,
Bob