Symmetrical Load Modulated Balanced Power Amplifier With Asymmetrical Output Coupling for Load Modulation Continuum

• Published in: IEEE transactions on microwave theory and techniques Vol. 70; no. 4; pp. 2315 - 2327
• Main Authors: Saad, Paul, Hou, Rui
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.04.2022; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Asymmetry; Balanced amplifier (BA); Broadband; Coupling; Couplings; Directional couplers; Doherty; energy efficiency; gallium nitride high electron mobility transistor (GaN-HEMT); Impedance; load-modulated balanced amplifier (LMBA); Modulation; Peak to average power ratio; power amplifier; Power amplifiers; Power generation; Radio signals; Transistors; Voltage
• ISSN: 0018-9480; 1557-9670
• DOI: 10.1109/TMTT.2022.3147843

This article presents a technique for load-modulated balanced amplifiers (LMBAs) to achieve a continuum of load modulation (LM) ratio. This has been possible in prior arts using asymmetrical auxiliary devices. In contrast, the proposed technique employs identical auxiliary devices. A LM ratio is enabled by a specific coupling factor of the power-combining coupler at the output. The proposed LMBA technique is demonstrated through the design, implementation, and measurement of a concurrent wideband LMBA operating across 3.1-4.2 GHz. The prototype achieves a peak output power of <inline-formula> <tex-math notation="LaTeX"> 48.1\pm 0.6~\text {dBm} </tex-math></inline-formula>, with drain efficiency of 47-58% at peak power and 47-61% at 10-dB power back-off. The concurrent wideband performance is demonstrated by a characterization with 900-MHz new radio (NR) signal with 10-dB peak-to-average power ratio (PAPR). At 37.8 dBm of average output power, the measurement yields 44% drain efficiency and −44-dBc adjacent channel leakage ratio (ACLR).