IP3 out of band - RF Cafe Forums

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john
Post subject: IP3 out of band
Unread postPosted: Mon May 30, 2005 5:56 am

What is the method to mesure and calculate Input IP3 Out of band,
meaning 2 signal out of the IF filter caused IM3 inband.

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Guest
Post subject:
Unread postPosted: Mon May 30, 2005 5:34 pm

You know, I think you need to create your own method but what about this:

Measure input tones trough a broadband directionnal coupler,

Measure inband IMDs at the output,

Divide by the gain the IMD products as measured at the output

The ratio of what measured at the input and the products is some sort of IMD measure.

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Guest
Post subject: IP3 "out of band"
Unread postPosted: Tue May 31, 2005 11:26 am

Umm - It appears the question is poorly put.

IP3 is the (hypothetical) point where the power in the 3rd order IM distortion products is equal to the power in the desired output. If there is zero desired output (as there will be if your filters are adequate), then there cannot be an IP3 as usually defined.

The previous respondent hinted at this when he said that you'd get "some sort of IMD measure" with the process he outlined.

If this measurement is for meeting a requirement, then you need to get the specifier to clarify the intent and execution of tests for this spec.

Good Luck!

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Gus
Post subject:
Unread postPosted: Thu Jun 09, 2005 9:57 pm
Offline
Lieutenant

Joined: Thu Jun 09, 2005 9:50 pm
Posts: 1
I may be failing to understand your question.

Are you talking about two out of band signals mixing and causing an unwanted inband signal? If so, can't you inject two tones into the part of the circuit you are concerned about?

Posted 11/12/2012