Theory and Implementation of a Load-Mismatch Protective Class-E PA System

Jeroen Ponte*, Ali Ghahremani, Maikel Huiskamp, Anne-Johan Annema, Bram Nauta

*Corresponding author for this work

    Research output: Contribution to journalArticleAcademicpeer-review

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    Abstract

    Highly efficient switch-mode class-E power amplifiers (PAs) are sensitive to load impedance variations. For voltage standing wave ratios (VSWRs) up to 10:1, the peak switch voltage and the average switch current can increase by a factor of 1.7 and 2.5, respectively, relative to those under nominal load conditions, imposing serious reliability risks. This paper describes a technique to self-protect class-E PAs to decrease their sensitivity to load variations, relying on the tuning of the switch-tank relative-resonance frequency, implemented by an on-chip switched-capacitor bank (SCB). To validate the technique, load-pullmeasurements are conducted on a class-E PA implemented in a standard 65-nm CMOS technology, employing an off-chip matching network, augmented with a fully automated self-protective control loop. Under nominal conditions, the PA provides 17.8dBm at 1.4GHz into 50 from a 1.2-V supply with 67% efficiency. The proposed self-protective PA can reduce its peak switch voltage below the technology- and switch designrelated limit for any load with a VSWR up to 19:1 while not considerably impacting output power and efficiency, which see a maximum degradation of 1.6dB and 6%, respectively. Furthermore, a class-E PA designed to safely handle 2.5× the nominal average switch current can reliably operate for VSWRs up to 19:1 when protected with our technique.
    Original languageEnglish
    Pages (from-to)369-377
    JournalIEEE transactions on circuits and systems I: regular papers
    Volume67
    Issue number2
    Early online date22 Jul 2019
    DOIs
    Publication statusPublished - 1 Feb 2020

    Keywords

    • CMOS integrated circuits
    • load mismatch
    • VSWR
    • power amplifiers (PAs)
    • class-E PA
    • Self-healing
    • self-protecting

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