The envelope tracking (ET) design methodology is routinely adopted to improve the efficiency of radio frequency power amplifiers (PAs). One short coming of state-of-the-art ETPAs is that their supply modulators are usually designed and optimized for a single communications standard. They are either incompatible in modern communication devices where multiple communications standards are used, and/or the efficiency unoptimized when the devices operate in standards other than the designed standard. To circumvent this shortcoming, a novel supply modulator for multistandard communications is proposed. The proposed design embodies a proposed dual-mode Sigma-Delta control block and an adaptive biasing Class AB amplifier, which allows the supply modulator self-adjusting its operation and optimizing the efficiency according to the application. A prototype supply modulator IC is designed and fabricated using a 180 nm CMOS process. Based on measurements, the proposed supply modulator features the highest static efficiency of 91% and the highest 3 dB backoff static and dynamic efficiency compared to the state-of-the-art supply modulators. When tracking 40 MHz LTE-A envelope signals, the prototype supply modulator achieves a high efficiency of 85% at 1.8 W output power, and the efficiency remains high >80% for a wide range of output power, from 0.5 to 1.8 W.
