An Envelope Tracking Power Amplifier Based on Gan Hemts

In modern communication systems, envelope tracking (ET) is an important technology which can improve the efficiency of radio frequency (RF) linear power amplifier (LPA) significantly. A DC/DC converter is utilized in this technology to modulate the supply voltage of LPAs. It makes the supply voltage waveform track the envelope signal, thus the efficiency of the LPA can be largely improved. To track the high bandwidth envelope signal, the switching frequency of the DC/DC converter must be extremely high. GaN HEMT is a wide band gap device with excellent switching performance, therefore it is an ideal power semiconductor device for this application. In this paper, a 2-phase interleaved Buck converter based on GaN HEMT is introduced, which operates as envelope tracking power amplifier (ETPA). A detail analysis of modulation strategy used in multiphase interleaved Buck converter will be proposed and the optimal one will be selected. Moreover, an appropriate design of output filter is given to ensure the envelope tracking accuracy. Simulation results are provided to support the analysis and design. Finally, the proposed method is also verified by experimental results acquired from a prototype with peak power up to 125W and bandwidth up to 200kHz.