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.
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.
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.
Thu Jun 09, 2005 9:57 pm
Thu Jun 09, 2005 9:50 pm
I may be failing to understand
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?