A Compact L-Band Reverse-Type Envelope Tracking System

This article presents the implementation and in-depth analysis of a compact
${L}$
-band reverse-type envelope tracking (ET) system comprising a floating-source RF power amplifier (PA) with a galvanically isolated gate supply and a reverse-topology buck converter as the envelope amplifier (EA). With the reverse buck (RB) converter switching at 80 MHz, the system accommodates signals with up to 20 MHz instantaneous bandwidth (IBW). Characterized by pulsed RF measurements and supplied from 40 V, it delivers 55.1-W saturated output power with up to 55.7% overall power-added efficiency (PAE). The best performance is achieved at 1.36-GHz carrier frequency. Alternative shaping functions (SFs) addressing maximum PAE, linear gain, and maximum power supply rejection ratio (PSRR) are extracted from these measurements. Under dynamic operation at 38.5-dBm average output power using a 16-MHz orthogonal frequency-division multiplexing (OFDM) modulated signal with 8.5-dB peak-to-average power ratio (PAPR), a PAE-optimized SF, and linearization by digital predistortion (DPD), the ET system shows 33.2% overall PAE. This is an improvement of 14.9 percentage points (%-points) compared with the PA operating with static 40-V supply. During all dynamic measurements, built-in test capabilities are used to investigate the interaction between the individual system parts and their influence on the linearizability of this unique and complex system.