Abstract
A novel predistortion technique using an automatic average-power bias controlled diode is proposed to compensate the complicated nonlinear characteristics of a microwave class-F power amplifier using an AlGaN/GaN HEMT. The optimum value for diode bias voltage is automatically set according to detected input average RF power level. A high-efficiency 1.9GHz class-F GaN HEMT power amplifier with the automatic average-power bias control (ABC) diode linearizer achieves an improved third order inter-modulation distortion (IMD3) of better than -45dBc at a smaller than 6dB output power back-off from a saturated output power of 27dBm, without changing drain efficiency. The adjacent channel leakage power ratio (ACPR) for 1.9GHz W-CDMA signals is below -40dBc at output power levels of smaller than 20dBm for the class-F power amplifier.
