Summary: Abstract--A high performance GaN HFET WCDMA
basestation power amplifier is presented, which uses an envelope
tracking bias system to achieve high linearity and efficiency. The
measured overall power-added efficiency (PAE) reached 50.7 %,
with a normalized power RMS error of 0.7% and ACLR of -52
dBc at an offset frequency of 5 MHz, at an average output power
of 37.2 W and gain of 10.0 dB for a single carrier WCDMA signal.
To the authors' knowledge, this corresponds to the best efficiency
reported for a single stage base station power amplifier. Digital
predistortion (DPD) was used at two levels: memoryless DPD to
compensate for the expected gain variation of the amplifier over
the bias envelope trajectory, and deterministic memory
mitigation, to further improve the linearity. The signal envelope
had a peak-to-average power ratio of 7.67 dB.
Index Terms-- Base station power amplifier, efficiency,
envelope tracking, digital predistortion, WCDMA, GaN HFET.
High power-added efficiency is an important objective for
base-station amplifiers, influencing thermal management,
reliability, and cost. It is challenging to maintain high