A High-Voltage-Enabled Class-D Polar PA Using Interactive AM-AM Modulation, Dynamic Matching, and Power-Gating for Average PAE Enhancement

This paper describes a 2.4-GHz digitally-modulated class-D polar power amplifier (PA) with novel circuit techniques to enhance the average power-added efficiency (PAE
_ave
) that becomes increasingly crucial to prolong the battery lifetime. The PA features 5+5-b interactive AM-AM modulation between the class-D unit amplifiers and a novel high resolution dynamic matching network (DMN) to improve the back-off PAE. A novel power-gating technique tailored for class-D PAs is also proposed and embedded into each unit amplifier and its driver (tapped inverter chain), alleviating leakage-current suppression, area reduction of the DMN, and direct-powering by a standard 1.5-V AA battery. An high back-off power efficiency is made possible by introducing a multi-bit capacitively-tuned DMN, which adds low loss while improving the PAE of the unit amplifiers using the load-pull optimization. The DMN also can correct the antenna impedance mismatch for better average P
_out
(P
_out,ave
) and PAE
_ave
under a practical VSWR (2.5:1), and aids to reconfigure the PA between the P
_out
-optimized and the PAE-optimized modes. For a 20-MHz 64-QAM OFDM output at a typical EVM (<; -25 dB), the 65-nm CMOS PA exhibits 40.7% PAE
_ave
at a 16.3-dBm P
_out
. The mode switching is demonstrated as a prospective function for battery lifetime extension.