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KCC's Quizzes: AQQ229 about IP3 lab measurement


IP3 (intercept point of order 3) is a spec one find in many RF component datasheet. It is directly linked with the linearity of a function behavior. 

More precisely, It indicates the amount of the intermodulation products of order 3 that interfere with the baseband.

The above pictures show the lab setup and a Spectrum Analyzer screenshot to measure the IP3 of a device (DUT) in the lab.


  1. What are the frequencies provided by sources 1 and 2?
  2. What is the IP3 measured in that test?

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[edited by: emassa at 5:46 PM (GMT -5) on 2 Mar 2023]
  • 1) Fundamental Freqs    f1= 1245 MHz, f2= 1255MHz

    2f1-f2= 1235 MHz,  2f2-f1= 1265 MHz 

    2) Delta -11dBm - (-45dBm) = 34dB = 2*(OIP3 - Pout) = 2 ( OIP3 - (-11dB) ) -- > OIP3 = 6dBm

    I believe this was a 7dB Gain device (forgotten to be mentioned in the text :-) )  Then IIP3= 6-7 = -1dBm 

       you find OIP3, not IIP3. Without OP-Gain info, we cant calculate IIP3 ;-)  

    Edit: Added IM3 Frequencies 2f2-f1 and 2f1-f2 Frequencies. 

  • If you know Pin, actually you can calculate IIP3. But in this case you're right, because the power used in the calculation is Pout (the only power known) so the calculated IP3 is OIP3. I will need to correct my answer. 

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