A GaN MMIC Dual-Asymmetrical-Lange-Coupler-Based Load-Modulated Balanced Amplifier for Back-Off Efficiency Enhancement

In this letter, a dual-asymmetrical-Lange-coupler-based load-modulated balanced amplifier (DALC-LMBA) topology is proposed for back-off efficiency enhancement. An input asymmetrical Lange coupler (ALC) is used to sequentially turn on the balanced amplifiers (BAs) for power back-off efficiency enhancement, another output ALC is adopted to generate proper load modulation (LM) for all three transistors. To verify the proposed design approach, a 23–25 GHz DALC-LMBA was implemented in a 0.12-
$\mu $
m gallium nitride (GaN) process. It achieves 34–34.5 dBm saturated output power with 18%–20% power-added-efficiency (PAE) and 14%–18% 8-dB back-off PAE across the band. When excited by a 200-MHz 7.2-dB peak-to-average power ratio 5G new radio (NR) signal with digital predistortion, it achieves 14.4%–18% average PAE and better than −41 dBc adjacent channel leakage ratio (ACLR).