High-Efficiency Outphasing-Like Coupler Combined Power Amplifiers for Wireless Base Stations

To efficiently amplify modulated signals with high peak-to-average power ratios (PAPRs) in modern wireless communication systems, outphasing power amplifiers (OPAs) are worth considering due to their high efficiencies at back-off. Conventional OPAs using an output Chireix combiner have limited bandwidth and back-off range. For the first time, two new outphasing-like topologies using coupler-based power combining techniques are proposed. Theoretical analysis provides a straightforward realization of OPAs without additional reactive compensation elements based on the output coupler, thus increasing the bandwidth, and significantly simplifying the OPA design procedures. For validation, the outphasing-like power amplifiers (OLPAs) I and II are designed using output branch-line and rat-race couplers with synthesized direct-matching networks (SDMNs) to obtain high drain efficiencies (DEs), respectively. The implemented OLPA I with measured peak output powers of 39.7–39.8 dBm achieves DEs of 61.3%–64.1% and 42%–48% at saturation and at 6-dB back-off from 3.4 to 3.5 GHz. Besides, the implemented OLPA II operates from 3.2 to 3.6 GHz with measured DEs of 61.8%–70% at saturation (43.5–44.3 dBm) and 41.5%–51.1% at 8-dB back-off.