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Summary: IEEE MICROWAVE AND GUIDED WAVE LETTERS, VOL. 8, NO. 3, MARCH 1998 121
Linear High-Efficiency Microwave Power
Amplifiers Using Bandpass Delta-Sigma Modulators
Arun Jayaraman, P. F. Chen, G. Hanington, L. Larson, and P. Asbeck
Abstract-- A novel amplifier configuration is described, in
which a bandpass delta-sigma modulator is used to produce a
two-level (digital) signal representing an analog radio frequency
(RF) input. Subsequently, a switching-mode amplifier and band-
pass filter are used to amplify the signal and remove unwanted
spectral components. This configuration has the potential of
achieving high efficiency (typical of switching mode amplifiers)
together with high linearity. A simulated implementation with
GaAs heterojunction bipolar transistors (HBT) is shown.
I. INTRODUCTION
THERE is significant interest in increasing the power-
added efficiency (PAE) of microwave power amplifiers
to address the needs of battery-operated communication sys-
tems. However, the most efficient microwave power amplifiers
operate in a switching mode, or at best in a nonlinear class of
operation [1], resulting in excessive spectral growth and loss
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