Multiple-input buck converter optimized for accurate envelope tracking in RF power amplifiers

Envelope Tracking techniques are used to increase the efficiency of modern radiofrequency transmitters. These techniques are based on varying the supply voltage of the radiofrequency power amplifier according to the envelope of the signal to be transmitted. This paper presents an Envelope Tracking system based on a multilevel topology that targets relatively low voltage systems (12-28 volt range) and medium to high power applications (> 50 W peak power). The proposed converter achieves low output voltage ripple, high tracking bandwidths, high efficiency and high output power capabilities. An appropriate characterization of the load behavior of the radiofrequency power amplifier allows the system to work in an open loop manner. This paper shows that the envelope tracking system proposed is capable of increasing the efficiency of linear, Class-A and Class-B commercial radiofrequency power amplifiers between 10 and 15%.