A High-efficiency Outphasing Power Amplifier Utilizing a Synthesized Direct-matching Technique based on Two-section Branch-line Coupler Output Combiner

To efficiently amplify modulated signals with high peak-to-average power ratios (PAPRs) in 5G and future 6G wireless communication systems, outphasing power amplifiers (OPAs) are worth considering due to high efficiencies at back-off. To simplify the OPA design process, a new output power combining approach is proposed that utilizes a branch-line coupler without additional reactive compensation elements. Theoretical analysis provides a straightforward realization, of OPAs after synthesized direct-matching networks (SDMNs) are used to conjugately match sub-PAs with the combiner. The implemented OPA with measured peak output power of 39.7-39.8 dBm achieves drain efficiencies (DEs) of 61.3%-64.1% and 42%-48% at saturation and at 6-dB OBO from 3.4 to 3.5 GHz. Under excitation of a 20-MHz 5G NR signal with 8-dB PAPR at 3.45 GHz, an average DE of 41% with an adjacent channel power ratio (ACPR) below -45.2 dBc is obtained using digital predistortion (DPD). © 2025 IEEE.