A Quadrature Digital Power Amplifier With Wide Efficiency Enhancement Coverage and High Dynamic Power Range
Yicheng Li, Yun Yin, Diyang Zheng, Fu Gao, Jie Lin, Zhen Hu, Ye Lü, Hongtao Xu
Abstract
A 15-bit quadrature digital power amplifier (DPA) is presented for wide efficiency enhancement coverage on the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">IQ</i> complex plane and high dynamic power range. Complex-domain Doherty is proposed with <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">IQ</i> -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 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">IQ</i> -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-mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\text{2}}$</tex-math> </inline-formula> 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 ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_{\mathbf{avg}}$</tex-math> </inline-formula> ), 25.3% average PAE with 70.4-dB dynamic power range, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 43.0-dB EVM floor at 2.4 GHz.