Third-order intercept point
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In telecommunication, a third-order intercept point (IP3 or TOI) is the point at which the linear extrapolation (as a function of input power) of linear output power and third-order distortion power level meet.
Important Notes:
- It is an extrapolated convergence--not directly measurable--of intermodulation distortion products in the desired output.
- It indicates how well a receiver performs in the presence of strong nearby signals.
- It is sometimes used (interchangeably with the 1 dB compression point) to define the upper limit of the dynamic range of an amplifier.
- Determination of a third-order intercept point is accomplished by using two test frequencies that fall within the first intermediate frequency mixer passband. Usually, the test frequencies are about 20 to 30 kHz apart.
Source: From Federal Standard 1037C and from MIL-STD-188
