N. Wolff and O. Bengtsson
Wiley Encyclopedia of Electrical and Electronics Engineering, J.G. Webster (Ed.). doi:10.1002/047134608X.W8394 (2019).
RF power amplifiers (PAs) are used in mobile communication networks for the amplification of the modulated RF signals. Linear RF PAs suffer from severe efficiency degradation if the output power is reduced and the PA is operated at power back-off.
Dynamic control of the RF PA supply voltage, that is, supply modulation, is an effective method to increase the PA efficiency at reduced output power. The variable supply voltage is generated by the so-called supply modulator. Designing of such modulators is a challenging task since a large bandwidth in combination with high output power is required. Several topologies for supply modulators have been developed in the past and intensively optimized. This article gives an overview of the available topologies, the challenges with each topology, and the performance of the systems.
Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Strasse 4, 12489 Berlin, Germany
RF power amplifier, supply modulator, envelope tracking
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