A 4-mm-Square Miniaturized Doherty Power Amplifier Module for W-CDMA Mobile Terminals(<Special Section>Analog Circuit Techniques and Related Topics)

概要

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Recently, the Doherty amplifier technique has been the focus of attention not only for base stations but also for mobile terminals because of its high power-added efficiency in the large back-off region. In this paper, we present a miniaturized Doherty power amplifier (PA) module for W-CDMA mobile terminals. The developed Doherty PA module consists of a 4-mm-square ceramic substrate (4.0mm×4.0mm×1.5mm, alumina, dielectric constant=8.8), a 1-mm-square GaAs MMIC (1.0mm×1.0mm×0.1mm), and 0603-size SMD passive components. To miniaturize the module size, the optimal designed quarter-wavelength transmission lines, which are used for impedance conversion for carrier amplifier output and phase compensation for peak amplifier input, are embedded in the ceramic module substrate. Two GaAs HBTs for a carrier amplifier and a peak amplifier and base bias circuits for each amplifier are integrated onto a single-chip GaAs MMIC. Measurement results at 1950MHz in a W-CDMA uplink signal indicate that 27dBm of the maximum output power, 45% of the power-added efficiency (PAE), 11dB of power gain, and 43% of PAE at 6dB back-off, i.e. 24dBm output power, are obtained with the developed Doherty PA. In other words, the PAE is improved from the theoretical PAE of a conventional class B amplifier, namely, from 23% to 43%. This is the smallest Doherty amplifier developed in the form of a module for mobile terminals.
社団法人電子情報通信学会の論文
2007-02-01