A High-Efficiency GaN Doherty Power Amplifier With Blended Class-EF Mode and Load-Pull Technique

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This brief presents a new Doherty power amplifier (DPA) configuration that employs high-efficiency switched-mode Class EF as its main and auxiliary cells. A blended approach is proposed to design the load network of the PA cells, in which the fundamental-frequency load impedance is obtained through load-pull analysis whereas the harmonic load impedances are set according to the Class-EF requirements. Realized using GaN HEMTs, the DPA prototype exhibits a drain efficiency (DE) of 81% at 45-dBm peak power and 68% at 6-dB back-off power, i.e., when excited using a 2.4 GHz continuous-wave signal. The proposed DPA has a 3-dB bandwidth of nearly 300 MHz within which the DE can be maintained above 68.5%. Using 16-QAM signal with 5-MHz bandwidth and 6-dB peak-to-average power ratio, the DPA shows a DE of 69.7% and an ACLR1 of -26.6 dBc at an average output power of 39.2 dBm.