Envelope Amplifier With Multiple-Linear Regulator for Envelope Tracking Power Amplifier

In this paper, a new envelope amplifier (EA) scheme incorporating a linear regulator array is presented. The proposed EA achieves a higher efficiency over a wide envelope range utilizing multiple linear regulators. The linear regulators biased as multiple supply voltages are responsible for delivering a partial envelope current, ensuring high efficiency. A simulation revealed the superior performance efficiency of the proposed scheme in terms of the instantaneous envelope voltage compared with that of a conventional EA. Based on the simulation results, an envelope tracking (ET) amplifier consisting of the proposed EA was implemented using a commercially available 60-W gallium-nitride (GaN) device. The experimental results show that the implemented ET system has an overall efficiency of 47.8% and a gain of 14 dB at an average output power of 40.8 dBm. In this situation, the spectral performance is less than -49.5 dBc using the optimum digital predisotortion functionality.