Varactor-Based Dynamic Load Modulation of High Power Amplifiers

TL;DR

This paper demonstrates the use of varactor-based tunable matching networks to dynamically load modulate high power amplifiers, significantly improving their efficiency at 1 GHz.

Contribution

It introduces a modular design approach with a quasi-static inverse model for efficiency optimization in load modulation of high power amplifiers.

Findings

Achieved 10-14% improvements in average PAE.

Validated dynamic tuning feasibility with a single carrier WCDMA signal.

Enhanced efficiency of class-E and class-J PAs at 1 GHz.

Abstract

In this work, dynamic load modulation of high power amplifiers using a varactor-based tunable matching network is presented. The feasibility of dynamic tuning and efficiency enhancement of this technique is demonstrated using a modular design approach for two existing high efficiency power amplifiers (PA), a 7-W class-E, and a 10-W class-J power amplifier PA at 1 GHz. For this purpose and for each of the PAs, a simple quasi-static inverse model is developed allowing an efficiency-optimized control of the PA and the varactor-based tunable matching network. Modulated measurements using a single carrier WCDMA signal with 11.3 dB peak-to-average ratio (PAR) indicate about 10 to 14 percentage units improvements in the average power-added efficiency (PAE) for the complete architecture.