A High Slew-Rate Adaptive Biasing Hybrid Envelope Tracking Supply Modulator for LTE Applications

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10 Scopus citations

Abstract

A linear-switch mode hybrid envelope tracking (ET) supply modulator utilizing adaptive biasing and gain enhanced current mirror operational transconductance amplifier (OTA) with class AB output stage in parallel with a switching regulator is presented. In comparison to a conventional OTA design with similar quiescent current consumption, proposed approach improves positive and negative slew rate from 50 to 93.4 V/μs and-87 to-152.5 V/μs , respectively, dc gain from 45 to 67 dB while consuming same amount of quiescent current. The proposed hybrid supply modulator achieves 83% peak efficiency, power-added efficiency (PAE) of 42.3% at 26.2 dBm for a 10-MHz 7.24-dB peak-to-average power ratio (PAPR) long-term evolution (LTE) signal and improves PAE by 8% at 6 dB back off from 26.2-dBm power amplifier (PA) output power with respect to fixed supply. With a 10-MHz 7.24-dB PAPR quadrature-phase shift keying LTE signal the ET PA system achieves adjacent channel leakage ratio (ACLR) of-37.7 dBc and error vector magnitude (EVM) of 4.5% at 26.2-dBm PA output power, while with a 10-MHz 8.15-dB PAPR 64QAM LTE signal the ET PA system achieves ACLR of-35.6 dBc and EVM of 6% at 26-dBm PA output power without digital predistortion. The proposed supply modulator core circuit occupies 1.1-mm2 die area, and is fabricated in a 0.18-$\mu \text{m}$ CMOS technology.

Original languageEnglish (US)
Article number7888538
Pages (from-to)3245-3256
Number of pages12
JournalIEEE Transactions on Microwave Theory and Techniques
Volume65
Issue number9
DOIs
StatePublished - Sep 2017

Keywords

  • Adaptive biasing
  • envelope tracking (ET)
  • gain enhancement
  • high slew rate
  • long-term evolution (LTE)
  • power amplifier (PA)

ASJC Scopus subject areas

  • Radiation
  • Condensed Matter Physics
  • Electrical and Electronic Engineering

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