Transfer characteristic of IM/sub 3/ relative phase for a GaAs FET amplifier

Measured transfer characteristic of relative phase of the third order intermodulation distortion (IM/sub 3/) of a GaAs FET amplifier is described. The measurement system and method are also described. For drives in the weakly nonlinear region, the measured relative phase of IM/sub 3/ is equal to that of carriers, and agrees with the analysis result based on Volterra-series representation. For drives in the saturation region, the measured relative phase of IM/sub 3/ versus the input power is larger than that of carrier´s relative phase. The measured results and the measurement method are useful for the design and adjustment of predistortion type linearizer for GaAs FET high power amplifiers.