Digital PA with voltage-mode topology using envelope delta-sigma modulation

A. Wentzel1, S. Hori2, M. Hayakawa2, K. Kunihiro2 and W. Heinrich1

Published in:

Int. J. Microwave Wireless Technolog., vol. 5, no. 3, 285-292 (2013).

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Abstract:

This paper reports on digital transmitter architecture for the 450 MHz band using an envelope delta-sigma modulator realized in CMOS and a voltage-mode class-S (VMCS) power amplifier (PA) based on GaN monolithic microwave integrated circuits (MMICs). The class-S PA is characterized for narrowband single-tone signals and a single- as well as a four-carrier downlink wideband code division multiple access (WCDMA) signal with a peak-to-average power ratio of 7.5 dB. Using single-tone excitation the PA shows a maximum drain efficiency of 86% and a peak output power of 4.4 W. At 6 and 10 dB back-off, 59 and 36% efficiency are achieved, respectively. With the single- and four-carrier WCDMA input signals maximum drain efficiencies of 64 and 53% are reached, respectively, and peak output power is 0.7 W. The adjacent channel leakage ratio shows values of about 234 dBc (5 MHz) and 238 dBc (10 MHz) for single-carrier WCDMA excitation. This is the first complete VMCS PA chain characterized with standard communication signals.

1 Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Straße 4, 12489 Berlin, Germany
2 NEC Corporation, Kawasaki, Kanagawa 211-8666, Japan

Keywords:

Microwave power amplifier, Class-S, Voltage-mode, Envelope delta-sigma, Modulation, GaN, MMIC.