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RF Burns

3rd Order Intercept Point

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        Say if I have two amplifiers connected in cascade with the following specifications:

Apmlifier 1:  Gain      Noise Figure      OIP3
                  15 dB          3 dB            15 dbm

Apmlifier 2:  Gain      Noise Figure      OIP3
                  15 dB          5 dB            20 dbm

Note:  OIP3 = third order intercept point.

I calculated the overall gain, the overall noise figure and the overall third order intercept point.

Overall gain = 30 dB

Overall noise figure = 3.146 dB

Overall OIP3 = 19.586 dBm  (= -10.414 dB)

My question is:  What does this level of OIP3 mean?  I know how to calculate it etc., but not what it actually means.  For example, what happens if my RF input was greater than 19.586 dBm??

Any details you can impart will be much appreciated.

RF Burns

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Google has many links to a definition of the 3rd Order Intercept Point. It basically is the output level where the intermodulation distortion becomes very noticeable and keeps increasing with increased output level.

Your circuit's gain is 30dB so the OIP3 output level is 19.586dBm, not the input level.

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