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Envelope tracking (ET) is a technique designed to enhance the efficiency of radio frequency power amplifiers (RF PA). It is based on providing the voltage to the RF PA with variations that mimic the shape of the envelope of the communication signal that the RF PA is processing. As the bandwidth of these signals can be around several megahertz, the switching frequency of the switching mode power supply designed for ET applications has to be very high. The good switching characteristics of Gallium Nitride devices makes them suitable for this application. This paper presents two multiphase converters to be used as envelope modulators in envelope tracking applications. [ABSTRACT FROM AUTHOR]

A dc–dc power converter based on a two-phase synchronous buck converter that reproduces single-carrier digital modulation schemes by controlling the first switching harmonic of the output voltage ripple is presented in this paper. The dc–dc power converter carries out both the lighting and the transmission functionalities of visible light communication transmitters. Control of both the amplitude and the phase of sinusoidal currents injected toward high-brightness LEDs enable the use of efficient modulation schemes, such as quadrature amplitude modulation, carrierless amplitude and phase modulation, amplitude-shift keying, and phase-shift keying. These modulation schemes achieve higher spectral efficiency (i.e., more data can be transmitted using the same bandwidth) than previously proposed modulation schemes performed by visible light communication transmitters based on the use of dc–dc power converters. To the authors' knowledge, the ratio between the bit rate achieved and the switching frequency of the dc–dc power converter presented in this paper is the highest that can be found in the literature. [ABSTRACT FROM AUTHOR]