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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?

Hide replies until user replies.
[edited by: emassa at 5:46 PM (GMT -5) on 2 Mar 2023]
• Right reaction Martin! You are not bad at all in RF!

• YES! Bravo Gaetano!

• OK, it's time to publish the official answers...

Solution:
1. The 2 sources have to inject the 2 tones with close frequencies: they are visible as M1 and M2 in the SS screenshot : 1.245 GHZ and 1.255 GHz (delta = 10 MHz)

2. Measured from the first source:
M1 + (M1‐M3)/2 = ‐10.9dBm +(‐10.9dBm – (‐45.2dBm))/2 = +6.25 dBm
Measured from the second source:
IP3=M2 + (M2‐M4)/2 = ‐11dBm + (‐11dBm – (‐44.9dBm))/2 = +5.95dBm
We can conclude the DUT IP3 is around +6.1 dBm

3. It’s the Output IP3 (measurement taken at the output of the DUT). It is thus OIP3
IIP3 can be deducted by OIP3 = IIP3 + Gain(in dB))

Big applause to our 4 winners (and especially for the non-RF engineers)!

1. Martin WALKER - ADI - Staff Field applications Engineer - Burnham, UK

2. Gaetano PIARINO - ADI - Key Account Manager - Milan - Italy

3. Hakan UENLUE - ADI - Technical Application Expert - Stuttgart - Germany

4. Mark CEE - ADI - Snr Systems Integration Engineer - Cavite - Philippines

Now, be prepared to tackle our next coming quiz AQQ230 !

• Forgat to mention, there is an article detailing that subject (how IP3 is built) :IP3 and Intermodulation Guide | Analog Devices