13.8 A 24dBm 2-to-4.3GHz wideband digital Power Amplifier with built-in AM-PM distortion self-compensation

Modern wireless systems often support multi-standards with spectrum-efficient modulation schemes such as 64QAM and 256QAM and high data-rates. This poses stringent requirements on RF Power Amplifiers (PAs) for their carrier bandwidth, linearity, modulation rate, and efficiency. Several multiband Analog PAs (APAs) and Digital PAs (DPAs) are recently reported. However, multiband APAs often suffer from low power efficiency [1]. Although current-mode DPAs achieve high efficiency, high output power (Pout), and compact designs [2], they typically exhibit excessive AM-PM distortions intrinsically due to the digital power cell operations. Thus, current-mode DPAs often need frequency-dependent AM-PM look-up-tables for pre-distortion and/or real-time phase cancellation, resulting in additional overhead and difficult implementation for high modulation rates [3,4].