Linear Hybrid Asymmetrical Load- Modulated Balanced Amplifier With Multiband Reconfigurability and Antenna-VSWR Resilience

This article presents the first-ever highly linear and load-insensitive 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 the load modulation behavior of H-ALMBA can be insensitive to load mismatch by leveraging bias reconfiguration and the intrinsic load-insensitivity of balanced topology. Specifically, the PA’s linearity and efficiency profiles can be maintained against arbitrary load mismatch through
$Z_{L}$
-dependent reconfiguration of CA supply voltage (
$V_{\mathrm {DD,CA}}$
) and turning-on sequence of BA1 and BA2. Based on the proposed theory, an RF-input linear H-ALMBA is developed with GaN transistors and wideband quadrature hybrids. Over the design bandwidth from 1.7 to 2.9 GHz, an efficiency of
$56.8\% - 72.9\%$
at peak power and
$49.8\% - 61.2\%$
at 10-dB PBO are measured together with linear AMAM and AMPM responses. In modulated evaluation with 4G LTE signal, an EVM of 3.1%, ACPR of −39 dB, and average efficiency of up to 52% are measured. Moreover, the reconfigurable H-ALMBA experimentally maintains an excellent average efficiency and linearity against arbitrary load mismatch at 2:1 VSWR, and this mismatch-resilient operation can be achieved at any in-band frequencies. The overall measured performance favorably outperforms the state-of-the-art.