Theoretical study of intermodulation distortion in nonlinear power amplifier has been done. It relates to a generation of second harmonics of input signal and allowed to present a new linearization principle of these devices, which is based on use of mentioned harmonics energy as a feedback signal. Calculations of impact of described mechanism upon signals of different digital modulation types have been conducted. Significant reduce (up to 25 dB) in crosstalk level has been reached. And 1dB compression level of amplifier output power has almost reached saturation point.