Wideband Hybrid Envelope Tracking Modulator with Hysteretic-Controlled Three-Level Switching Converter and Slew-Rate Enhanced Linear Amplifier

Parisa Mahmoudidaryan, Debashis Mandal, Bertan Bakkaloglu, Sayfe Kiaei

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

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 VCF 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/μs 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%.

Original languageEnglish (US)
Article number8863502
Pages (from-to)3336-3347
Number of pages12
JournalIEEE Journal of Solid-State Circuits
Volume54
Issue number12
DOIs
StatePublished - Dec 2019

Keywords

  • 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)

ASJC Scopus subject areas

  • Electrical and Electronic Engineering

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