Circuits and system design of RF polar transmitters using envelope-tracking and SiGe power amplifiers for mobile WiMAX

Yan Li, Jerry Lopez, Donald Y.C. Lie, Kevin Chen, Stanley Wu, Tzu Yi Yang, Gin Kou Ma

Research output: Contribution to journalArticlepeer-review

49 Scopus citations

Abstract

This paper discusses the circuits and system design methodology of a highly-efficient wideband RF polar transmitter (TX) using the envelope-tracking (ET) technique for mobile WiMAX applications. Monolithic power amplifiers (PAs) are designed and fabricated in IBM 0.18 μm SiGe BiCMOS technology, and a linear-assisted witch-mode envelope amplifier is applied to modulate the PA supply voltage to form the core of the RF polar TX. Nonlinearities caused by bandwidth limitation of the envelope amplifier and timing misalignment have been investigated. When driven by WiMAX 64QAM 8.75 MHz signals, the overall PAE of our ET-based polar TX system reaches 30.5% at 17 dBm average output power, while also meeting the stringent WiMAX linearity specs without using any predistortion. When the decresting algorithm using the soft limiter is applied to the baseband, the overall PAE increases to 33%, at the expense of a higher EVM of 4.9%. Based on measurement results, our ET-based polar TX system has demonstrated excellent efficiency with good linearity for high peak-to-average ratio (PAR) broadband signals when compared with the recent literature on state-of-the-arts polar TX designs.

Original languageEnglish
Article number5648389
Pages (from-to)893-901
Number of pages9
JournalIEEE Transactions on Circuits and Systems I: Regular Papers
Volume58
Issue number5
DOIs
StatePublished - 2011

Keywords

  • Decresting algorithm
  • SiGe power amplifier (PA)
  • envelope-tracking (ET)
  • linear-assisted switch mode envelope amplifier
  • polar transmitters
  • power-added efficiency (PAE)

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