Reconfigurable Hybrid Asymmetrical Load Modulated Balanced Amplifier with High Linearity, Wide Bandwidth, and Load Insensitivity

This paper presents the first-ever load-insensitive and highly linear three-way load-modulation power amplifier (PA) based on reconfigurable hybrid asymmetrical load modulated balanced amplifier (H-ALMBA). Through proper amplitude and phase controls, the carrier, control amplifier (CA), and two peaking balanced amplifiers (BA1 and BA2) can form a linear high-order load modulation over wide bandwidth. Moreover, it is theoretically unveiled that once CA reaches saturation at the pre-determined power back-off (PBO), its current- and voltage-source duality makes the primary (BA1) and secondary (BA2) peaking amplifiers have complementary load dependence. As such, the PA’s linearity and efficiency profiles can be maintained against arbitrary load mismatch through Z
L
-dependent reconfiguration of CA supply voltage (V
DD,CA
) and turning-on sequence of BA1 and BA2. Based on the proposed theory, an RF-input H-ALMBA is developed with GaN transistors and wideband quadrature hybrids. Over the design bandwidth from 1.7-2.9 GHz, an efficiency of 57%-72% at peak power and 43%-53% at 10-dB PBO are measured together with linear AMAM and AMPM responses. In modulated evaluation with 4GLTE signal, an EVM of 3.1%, ACPR of −39 dB, and average efficiency of up to 52% are measured, which are well sustained against 2 : 1 VSWR of load through reconfiguration.