2018 Volume 15 Issue 19 Pages 20180845
This paper proposes a harmonic controlled symmetric Doherty power amplifier (DPA) for large back-off applications. For efficiency enhancement, the harmonic impedances of the carrier and peaking amplifiers are controlled in the continuous class-F mode. To extend the back-off range, unlike the traditional DPA, the output impedance of the peaking amplifier locates far away from infinity at the edge of the Smith chart, which can further improve the efficiency of the carrier amplifier. For verification, a 3.3–3.8 GHz symmetric DPA was designed and measured. The designed DPA can deliver an efficiency of 45%–48% at 9 dB back-off power over the whole frequency band with a maximum output power larger than 44 dBm. When driven by a 40-MHz modulated signal, the DPA exhibits an adjacent channel leakage ratio of better than –50 dBc after linearization at an average output power of 36.5 dBm.
