Forums › VSG Series Discussions › Cleaning IMD3 in multitone signal generation using VSG60A
- This topic has 4 replies, 3 voices, and was last updated 1 year, 7 months ago by Justin Crooks.
GSinghParticipantGSingh October 22, 2021 at 4:45 am
I am working on SFDR measurement using VSG60A and SA124B. While trying to generate 2-tone signal, i am getting IMD3 especially if I increase the power beyond -20dB. How can we ensure these frequencies are not generated by the VSG60A. A image of the dual tone signal is attached for reference.
AndrewModeratorAndrew October 22, 2021 at 10:19 am
Are you able to upload a smaller picture? It rejected your picture based on file size.
Justin CrooksModeratorJustin Crooks October 22, 2021 at 10:28 am
To determine whether the IMD3 products are from the generator or the analyzer, change the reference level on the analyzer by 10 dB. This will increase attenuation by 10 dB. If the levels stay the same they are from the generator. If they change significantly they are from the analyzer.
GSinghParticipantGSingh October 22, 2021 at 10:59 pm
The IMD3 are from the generator. As i also saw the output in another SA and those products are also there.
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Justin CrooksModeratorJustin Crooks October 25, 2021 at 9:52 am
Yes, those IMD3 products appear to be from the generator, at typical values. Typically you will see -50 dBc below -10 dBm, but it will get worse as you increase amplitude.
If you need two-tone better than -50 dBc, you would probably want 2 generators and a directional combiner. There are digital techniques as well, but they will be less stable over temperature and frequency.
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