GaN Envelope Tracking Power Amplifier with More Than One Octave Carrier Bandwidth

A high efficiency envelope tracking power amplifier which operates over the carrier frequency range of 500 MHz to 1.75 GHz is reported. The amplifier employs a single integrated circuit (IC) GaN RF PA which achieves greater than 12 W output power with greater than 50% drain efficiency under CW excitation. When used in the envelope tracking system with a 6.6 dB PAPR downlink single-carrier WCDMA signal, the GaN PA IC achieves 4 W of output power with 31% system efficiency (RF PA achieved 58.5% drain efficiency) at 752 MHz. Across the frequency range 500 MHz to 1.75 GHz, greater than 2 W with greater than 25% efficiency was demonstrated for the same WCDMA signal using the same configuration and biases for the RFPA and envelope amplifier, without changing impedance matching as the RF center frequency was tuned across the band. To the best of the author's knowledge, this is the first report of an envelope tracking power amplifier operated over carrier frequencies covering more than one octave range.