A FR3, 25 dBm Unbalanced MMIC GaAs Doherty Power Amplifier with Auxiliary Gate Voltage Modulation for Linearity Improvement

This paper presents a compact and fully monolithically integrated unbalanced Doherty power amplifier (DPA) for the FR3 mid-band spectrum, implemented in the WIN Semiconductors PQH1-0P 180 nm E-mode GaAs pHEMT technology. The design absorbs the intrinsic device output capacitance, C<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">out</inf>, using a parallel inductor in the Doherty combiner network to enhance bandwidth (BW). The asymmetric structure helps to improve output back-off (OBO) performance by more than 7 dB and makes it suitable for high peak to average power ratio (PAPR) signals. The DPA was evaluated under different auxiliary gate voltages to find the proper function as a gain enhancement technique in the saturation region to improve linearity. The DPA demonstrates a maximum small signal gain of 12.8 dB at 7.3 GHz, an output power of 23 – 24.5 dBm at saturation, a saturation drain efficiency (DE) of 45 - 57% and a 7 dB back-off DE of 30 - 45% over the BW from 7.3 to 8.7 GHz, which is equal to 17.5% fractional bandwidth (FBW), with a compact size of 2.5 mm × 2 mm.