Design Guidelines for Optimal Implementation of Doherty Power Amplifiers Based on Three-λ/4 Output Combiners

This work presents a design methodology for Doherty power amplifiers (DPAs) exploring two different topologies of output combiners composed of three λ/4 transmission lines. By imposing specific matching conditions in the theoretical analysis, design charts are derived to guide the selection of the optimal DPA configuration, starting from predefined target specifications. The theoretical findings are leveraged to design an integrated DPA in GaAs HBT technology for sub-6-GHz applications. The DPA achieves a peak output power of 33 dBm, with a power-added efficiency (PAE) and gain higher than 23% and 25 dB at 6 dB back-off, respectively, while maintaining a flat response with less than 0.5 dB ripple over 5–6 GHz. When measured with an 80-MHz-instantaneous bandwidth (BW) 1024-QAM 802.11ax signal, the DPA achieves an average output power of 22 dBm and a PAE of 12.5% at 3% error vector magnitude(EVM).