Analysis of envelope signal injection for improvement of RF amplifier intermodulation distortion

Adaptive bias techniques based on envelope signal power detection have been proposed for linearity enhancement and DC current reduction in RF amplifiers. Experimental results show an improvement in amplifier linearity, although asymmetric intermodulation distortion (IMD) was observed. This paper studies the effects of the magnitude and phase of the envelope signal injection on amplifier linearity, and illustrates a technique in which the IMD can be optimally cancelled.