Hi Erik

WOW !!

Kind regards

Kurt

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This shows the measurement option to measure OIP3 and it is used to measure the internal IIP3 at 0dB attenuation.
Two tones (6MHz and 7MHz) from fairly clean signal generators are used.
Bot the left and right IIP3 are shown.
Investigations are ongoing to further improve this and an IIP3 level of +25dBm could be possible.

Hi Erik
I have a few comments/suggestions.
I do not know how you test setup was, but there is a need to ensure the IIP3 level is not influenced by cross modulation between the two signal generators. The power combiner from the two generator ought to have as high isolation as possible between the two input ports, so the test signal from one signal source is not feed directly to the ?second signal source. Next it is common practice that the level from the two signal source are identical and thus the two sidebands are more equal, too to facility the calculation as half power of side tone + the test signal level.
I used some Mini Circuit power combiners with isolation and I also did build a few as described by N2PK Paul for his N2PK VNA, going down to fairly low frequencies.

I used the reflection bridge PCB seen om the link ?? and I did purchase these separately as an add on although not listed as a separate item. where I used the SMD type of T1-T6 transformers. Inspiration came from

In addition a video from National Instrument is quite good to watch ??

In this video you get a method how to figure out if it is the Signal Generators are reducing the IIP3 measurements or not, by adding attenuation in front of the SA. You have enough dynamic range to use some 10dB attenuation or maybe more in front of the SA.

Kind regards

Kurt

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Kurt,
Can you confirm I'm doing the IIP3 measurement as it should be done?

Hi Erik

Agree, removing any additional contribution on the two sideband frequencies from the two signal generators by using power combiners with isolation and other means such as isolators, will improve the displayed IIP3.

So bottom line it can only be better than what you see. However the signals must still be within the mixer linear range without compression and 0 dBm is maybe on the brink

Kind regards

Kurt

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But the internal generated IIP3 can not be higher then what is measured so I assume this measurement set a lower limit for the IIP3 of the tinySA, it could even be better. Correct?