Abstract: Based on an architecture model of a two-tone signal, we analyze the effects of the finite envelope modulator bandwidth and differential delay between envelope signal and RF phase signal on the intermodulation distortion (IMD), and derive a general simplified model that is much closer to laboratory measurements. This model overcomes the limitation of Raab’s model, which can only solve two specific instances:zero differential delay and infinite bandwidth of the envelope path. A contour map derived from the general model can help designers choose circuit parameters quickly and accurately. Finally, an envelope elimination and restoration RF power amplifier (EER RF PA) operating at 935MHz with a GSM/EDGE signal source is applied to demonstrate how to use the analysis method presented here.

Key words: RF, power amplifiers, intermodulation distortion, linearity