A Quadrature Digital Power Amplifier With Wide Efficiency Enhancement Coverage and High Dynamic Power Range

Abstract

A 15-bit quadrature digital power amplifier (DPA) is presented for wide efficiency enhancement coverage on the IQ complex plane and high dynamic power range. Complex-domain Doherty is proposed with IQ-cell-sharing and single-supply Class-G techniques to provide 32 power-added efficiency (PAE) peaks, good linearity, and simplified power management design. The efficiency enhancement and average efficiency of modulation signal can be verified and evaluated by a theoretical analysis using a switched-capacitor power amplifier (SCPA) model. The special control logic scheme enabling the combination of IQ-cell-sharing and Class-G techniques is implemented at a low cost. Fabricated in a 28-nm CMOS technology, the proposed DPA occupies a 0.74-mm2 compact die size with a single-transformer footprint. The DPA achieves a peak output power of 29.9 dBm with a PAE of 38.0% at 2.3 GHz. For long-term evolution (LTE) 20-MHz 64-QAM signal, the DPA obtains 24.5-dBm average output power ( Pavg), 25.3% average PAE with 70.4-dB dynamic power range, and −47.3-dB error vector magnitude (EVM) floor at 2.3 GHz. For the 802.11ax 40-MHz 256-QAM signal, it achieves 19.3-dBm Pavg, 19.2% average PAE with 50.4-dB dynamic power range, and −43.0-dB EVM floor at 2.4 GHz.