Variable gain active predistorter with linearity enhancement for a 2.4 GHz SiGe HBT power amplifier design

This paper proposes a 2.4 GHz SiGe HBT differential power amplifier (PA) with a novel on-chip variable gain active predistorter (PD) for linearity enhancement. The fully differential active PD provides an open collector adaptive bias control which can effectively enhance the linearity while improve power added efficiency (PAE). The PA with active PD achieves an output 1-dB compression (OP1dB) of 20 dBm, a gain control range of 10 dB, a PAE of 30%, and an error vector magnitude (EVM) improvement of 2.4 % under OFDM/64-QAM modulation signal. The fabricated die size including pads is less than 0.74 mm² and suitable for highly integrated linear PA.