Multilevel outphasing system using six-port modulators and doherty power amplifiers

In this paper, a simple and efficient architecture for implementation of multilevel outphasing systems is presented. The architecture consists of a six-port modulator and a Doherty power amplifier in each outphasing branch. Pin diodes are used as variable impedances of the six-port modulator and their parasitic elements are analytically compensated. A prototype of the variable load is fabricated and the results show the effectiveness of compensation method to prepare pin diodes as variable loads for a six-port modulator. As a proof of concept, a standard 2.4 GHz Doherty power amplifier is designed with 65% efficiency at peak power and 46% efficiency at 6 dB back off. The proposed system is simulated in advanced design system using a 20 MHz WLAN signal with 7.5 dB PAPR and 5 level outphasing. Simulation results show 31.6% power added efficiency for the Doherty-Outphasing system.

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