Supply modulator for envelope-tracking operation of dual-mode handset power amplifier

This paper presents a supply modulator for envelope-tracking (ET) operation of a dual-mode power amplifier (PA) for handset application. For stable operation of the supply modulator with different loads in the two power-modes, the buffer size is adjusted with the mode change. The power transistor size of switcher is also adjusted to increase the efficiency of the supply modulator for the each power-mode. The inductance in the switching amplifier is increased to avoid the distortion and to increase the efficiency in the low power-mode. An envelope shaping method of the sweet spot tracking is employed for ET operation of the dual-mode PA. For a 10-MHz long term evolution signal having a peak-to-average power ratio of 6.44 dB, the ET PA delivers a power-added efficiency (PAE) of 38.2%, an evolved universal terrestrial radio access adjacent channel leakage ratio of -35.6 dBc, and an error vector magnitude of 3.53% at an average output power of 27 dBm and an operating frequency of 1.71-GHz. For the low power-mode, the ET PA also delivers a PAE of 30% at an average output power of 17 dBm.