Load-Modulated Balanced Amplifiers for Next-G Wireless Communications

This article presents an overview of the recent advances in load-modulated balanced amplifier (LMBA), which has been a highly popular topic in RF research. The theory and design equations are revisited for different types of couplers, which were typically not distinguished in existing literature. Moreover, the design methodology is re-developed based on signal-flow analysis of individual balanced amplifier (BA) and control amplifier (CA) paths, indicating the intrinsic wideband nature of LMBA. Furthermore, LMBA design space are expanded with various modes showing highly desirable features for emerging wireless applications, including power back-off (PBO) range, linearity and insensitivity to load (antenna) impedance variations. A few realistic design examples are experimentally demonstrated to showcase the advantages of LMBA over state-of-the-art and the promising potential for next-G communications.