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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.

Questions:

  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]
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  • 1. The frequencies are f1=1245MHz, f2=1255MHz. f3=1235MHz and f4=1265MHz are IM products (2*f1-f2 and 2*f2-f1)

    2.  Supposing the input level is well below P1dB, you can calculate IIP3 by adding to the input power level the difference (divided by 2) between the fundamental signal at the output and the IM levels (everything in dB). So: IIP3=34/2 - 11=6dBm

  • Clarification on answer 2:

    6dBm is the OIP3 value not the IIP3.  

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