Intrinsically Mode-Reconfigurable Load-Modulation Power Amplifier Leveraging Transistor’s Analog-Digital Duality
This paper presents a new way of designing multi-mode switchable power amplifier without relying on any extra tuning elements. By operating the RF GaN transistor as a switch (digital) or amplifier (analog), it enables three different modes within a quadrature-balanced load-modulation architecture, including series/parallel Doherty and hybrid load modulated balanced amplifier (H-LMBA), which can be optimally configured according to different load conditions. Based on this new method, an intrinsically mode-switchable load-modulation PA is designed with GaN transistors and branch-line quadrature coupler at 1.7 GHz. Together with the unique harmonic-tuned method, the nominal mode of H-LMBA (for matched condition) achieves a high-order load modulation with > 62% measured efficiency across a 10-dB output back-off (OBO) range. Efficient performance is also demonstrated at series/parallel Doherty modes, which are configured with exchangeable main/auxiliary roles and dedicated switch settings offering mismatch resilience.