Optimized Design of GaN Switching Capacitor Based Envelope Tracking Power Supply for Satellite Applications

Abstract

In modern communication system, both the bandwidth and peak-to-average power ratio of the transmitted signal are increasing rapidly. As a result, the power amplifiers based on linear power amplifiers such as class A, B or AB suffer from very low efficiency. The most promising solutions are the Envelope Tracking (ET) and Envelope Elimination and Restoration (EER) techniques, which can greatly improve the efficiency by employing a dynamic power supply that tracks the envelope of the transmitted signal. This paper presents an implementation of the ET power supply based on a multilevel converter in series with a linear regulator for a satellite application. The multilevel converter consists of a switching capacitors based converter in order to have highly efficient and light solution because the weight of power supply, together with its efficiency, is of the outmost importance for the application. A prototype capable of following a 5MHz RF envelope signal with maximum output power of 40W is fabricated. The experimental results verify the effectiveness of the proposed solution with 96.15% efficiency for the multilevel converter and 75% for the ET power supply. Furthermore, an experimental comparison between Silicon and GaN transistors is conducted in order to verify the benefits of GaN transistors.