A Watt-Level Phase-Interleaved Multi-Subharmonic Switching Digital Power Amplifier

This article presents a multi-subharmonic switching (SHS) digital power amplifier (PA) architecture for enhancing power back-off (PBO) efficiency while achieving watt-level output power. The proposed phase-interleaved architecture provides the inherent cancellation of the subharmonic components in the PBO region, alleviating the burden of the matching network. The proposed multi-SHS scheme can be further combined with a class-G operation to create a greater number of efficiency peaks in the PBO region. A transformer-based, three-way power combiner and a triple-stacking class-D driver are utilized to obtain watt-level output power. The proof-of-concept PA prototype is implemented with a switched-capacitor PA (SCPA) architecture in 65-nm CMOS and achieved 30-dBm peak power at 1.9 GHz, with 45.9%/41.3%/35.3%/32.2%/24.2% drain efficiency located at 0-, -3.5-, -7.0-, -9.5-, and -12-dB PBO, respectively. The average efficiency was 31.4% in real-time operation with a 7.2-dB peak-to-average power ratio (PAPR) modulated signal.