High-Efficiency Asymmetric Doherty Power Amplifier with Spurious Suppression Circuit

Abstract

A high-efficiency asymmetric Doherty power amplifier has been developed. This study proposed a harmonic suppressing technique at the second and the third harmonics and an impedance converting technique at a fundamental frequency with a T -shaped stub. Amplification efficiency was improved by a two-power-level impedance optimisation and harmonic treatment for the carrier amplifier and peaking amplifier on an asymmetric Doherty power amplifier circuit. The 10-W and 45-W GaN HEMTs released by Cree/Wolfspeed are respectively used for the carrier amplifier and the peaking amplifier. The fabricated asymmetric Doherty power amplifier with 58.6 % drain efficiency at a saturated output power of 46.3 dBm was achieved at 2.19 GHz. It achieved a 72.1 % drain efficiency at 8 dB output back-off condition from the saturation. Furthermore, the second and third harmonic spurious levels were reduced to −58.1 dBc and −62.8 dBc, respectively.