A high-efficiency supply modulator with a highly-linear envelope detector for WCDMA envelope-tracking applications

This paper presents a high-efficiency supply modulator (SM) for WCDMA envelope-tracking power amplifier (ET PA) system. An on-chip highly-linear envelope detector is employed so that no extra envelope signal from baseband is needed. The proposed SM chip reduces the complexity of ET technique application. It can be directly employed in transmitters without using other programming or elements. It is shown that the proposed SM linearly tracks WCDMA single carrier envelope signal and achieves an efficiency of 76%. The supply modulator was fabricated in a standard 180-nm CMOS technology. The die area is 0.7 by 0.7 mm2, and it consumes 18.2-mW of power at 3.3-V power supply.