RF Class-S Power Amplifiers: State-of-the-Art Results and Potential

Published in:
IEEE MTT-S Int. Microw. Symp. Dig., Anaheim, CA, May 25-27, pp. 812-815 (2010).
© Copyright Copyright 2009-2010, IEEE MTT. All Rights Reserved. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.

Abstract:
This paper reports recent results on a current-mode class-S power amplifier for the 450 MHz band, based on GaNHEMT MMICs. We achieve a peak output power of 8.7 W for a single tone at 420 MHz, encoded in standard band-pass deltasigma modulation with 1.68 Gbps sampling frequency. The respective efficiency is 34%. We find that these values strongly vary with coding efficiency of the modulation and reach 19 W with 59% for square-wave excitation. In order to clarify the potential of the PA in more detail, the S-class characteristics at power back-off and with varying oversampling ratio are presented as well.

Keywords:
power amplifier, class-S, GaN, HEMT, switchmode, band-pass delta-sigma modulation.

Full version in pdf-format.