Wideband harmonically-tuned GaN Doherty power amplifier

This paper presents the design of a wideband harmonically-tuned Doherty amplifier. The frequency-dependent back-off efficiency degradation was minimized by compensating the effect of the frequency-sensitive impedance inverters over the design band. Suitable choice of device size ratio as well as harmonic load tuning at back-off and maximum power operations were also considered, resulting in superior performance over the targeted design band. The maximum output power ranged from 48.2 dBm to 49.6 dBm. 6 dB back-off efficiencies of η6dB≥53 % (power-added efficiency PAE≥50 %) were measured over 1.7–2.25 GHz (28 % bandwidth). When linearized using digital pre-distortion (DPD), the Doherty amplifier had adjacent-channel leakage ratio (ACLR) of −43 dBc for a long-term evolution (LTE) signal at 1.85 GHz (η=50 %) and −44 dBc for a wideband code-division multiple access (W-CDMA) signal at 2.11 GHz (η=41 %), at average output power of 41.0 dBm and 40.5 dBm, respectively.