期刊
IEEE JOURNAL OF SOLID-STATE CIRCUITS
卷 54, 期 12, 页码 3336-3347出版社
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
DOI: 10.1109/JSSC.2019.2941014
关键词
Envelope tracking (ET); hybrid; hysteresis control; long-term evolution (LTE); LTE-advanced; power amplifier (PA); slew-rate enhancement (SRE); supply modulator; three-level switching converter (3L-SWC)
资金
- Qualcomm Inc., San Diego, CA, USA
- National Science Foundation Connection One Center, Arizona State University, AZ, USA
A wideband hybrid Envelope tracking (ET) modulator utilizing a hysteretic-controlled three-level switching converter (3L-SWC) and a slew-rate enhanced linear amplifier (LA) are presented. In addition to smaller ripple and lower losses of 3L-SWCs, employing the proposed hysteresis control loop results in a higher speed loop and wider bandwidth converter, enabling over 80 MHz of switching frequency. A concurrent sensor circuit monitors and regulates the flying capacitor voltage V-CF and eliminates the conventionally required calibration loop to control it. The hysteretic-controlled 3L-SWC provides a high percentage of power amplifier (PA) supply load current with lower ripple, reducing the LA high-frequency current and ripple cancellation current, improving the overall system efficiency. A slew-rate enhancement (SRE) circuit is employed in the LA, resulting in slew rate of over 307 V/mu s and bandwidth of over 275 MHz for the LA. The SRE circuit provides a parallel auxiliary current path directly to the gate of the class-AB output stage transistors, speeding-up the charging or discharging of output without modifying the operating point of the remaining LA, while maintaining the quiescent current of the class-AB stage. The supply modulator is fabricated in a 65-nm CMOS process. The measurement results show the tracking of long-term evolution (LTE)-40-MHz envelope with 93% peak efficiency at 1-W output power, while the SRE is disabled. Enabling the SRE, it can track LTE-80-MHz envelope with peak efficiency of 91%.
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