A Broadband Inverse-Balun Load-Modulated Power Amplifier (IBMA) Covering 1.3–3.3 GHz

This paper presents a new class of load-modulated power amplifiers (PAs), named as the inverse-balun load-modulated power amplifier (IBMA). For the first time, it is discovered that one coupled-line-based balun topology can be reconfigured from a 180° power combiner to a 0°power combiner by performing the short-to-open transformation at each termination. Building on this newly identified 0° power divider/combiner, the IBMA is introduced. Similar to existing load-modulated PAs, IBMA employs one main amplifier and one auxiliary amplifier with Doherty-like biasing. However, unlike conventional Doherty PAs or load-modulated balanced amplifiers (LMBAs), the IBMA achieves ultra-wide bandwidth using only two transistors as the core amplifying blocks. To validate the proposed architecture, a GaN-based IBMA prototype is designed and fabricated on PCB, covering 1.3–3.3 GHz. Experimental results demonstrate a peak output power efficiency of 40–61%, 6-dB output back-off (OBO) efficiency of 40–53%, and an output power of 41–44 dBm across the band.