Broadband High Efficiency Post-matching Doherty Power Amplifier Based on Mixed-Topology

In this paper, a broadband and high efficiency post-matching Doherty power amplifier (PMDPA) based on a mixed-topology is proposed. The gate bias is set to give a smaller conduction angle for the carrier device and a deep Class-C mode for the peaking device to realize a high back-off efficiency. A “ \pmbπ type” harmonic injection network allows the second harmonic components of two active devices to be mutually injected, thus achieving waveform amplitude modulation (WAM). This mitigates the deteriorated performance caused by the employed gate bias settings. Moreover, a coupled phase compensation network is used to compensate for the loss in bandwidth caused by this harmonic injection network. For demonstration purposes, a high efficiency Doherty prototype is devised based on two identical 10W GaN HEMTs. Measurement results show that a drain efficiency of at least 60% is achieved at 5.3-6 dB back-off power from 1.4 to 2.1 GHz.