Antenna-VSWR-Resilient Load-Modulation Power Amplifiers for 5G-and-Beyond Communications

Load modulation has been a compelling technology for high-efficiency power amplification of spectrally-efficient modulated signals. However, conventional Doherty power amplifiers (PAs) face limitations including restricted bandwidth, a limited dynamic range, and high sensitivity to load impedance mismatch. In emerging 5G systems, fluctuations of the antenna impedance are inevitable due to beamforming and steering using large antenna arrays. In this presentation, I will introduce a series of load-insensitive load-modulation PAs based on a quadrature-balanced topology, including quasi-balanced Doherty PA (QB-DPA) and load-modulated balanced amplifier (LMBA). By leveraging quadrature balance and intrinsic varactor-less reconfigurability, the QB-DPA and LMBA can both maintain the wideband efficiency and linearity performance against arbitrary antenna impedance variations up to 3:1 VSWR. Moreover, a novel load-modulated double-balanced amplifier (LMDBA) will be presented, which is endowed with an inherent isolation from the antenna. This innovation holds promise for eliminating the need for magnetic circulators that are widely deployed in current 5G massive MIMO systems.