Multilevel Supply-Modulated Chireix Outphasing With Continuous Input Modulation

Tommaso Cappello*, Taylor Wallis Barton, Corrado Florian, Michael Litchfield, Zoya Popovic

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

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Abstract

This paper presents a dynamic characterization of a multilevel (ML) Chireix outphasing (ML-CO) power amplifier (PA) with modulated signals. The ML-CO technique combines the advantages of envelope tracking and outphasing architectures by limiting the supply modulation to discrete levels with an efficient power-DAC modulator and using outphasing for fine amplitude control. We describe an experimental test bench that supplies the required phase- and time-aligned modulated signals for outphasing and supply modulation simultaneously. Pulsed characterization is used to design an ML memoryless polynomial DPD. The linearized ML-CO GaN X-band MMIC PA is demonstrated with fixed input drive levels for 9.3-dB peak-to-average power ratio (PAPR), 1.4-MHz and 11.3-dB PAPR, 10-MHz LTE signals with a 9.7-GHz carrier. For both signals, the average total power consumption is reduced by a factor of two when supply modulation is used. An investigation of control signal generation strategies is presented, including combinations of discrete supply and continuous input modulation. A simple exponential function tracks the optimal efficiency trajectory of the ML-CO PA, enabling overall efficiency improvements within 9 and 27 percentage points. This control strategy is applied to radar pulses with amplitude shaping and frequency chirp, with the efficiency improvement of up to 11.8 percentage points compared with constant-supply operation, with 29-dB improvement in spectral confinement.
Original languageEnglish
Pages (from-to)5231-5243
Number of pages13
JournalIEEE Transactions on Microwave Theory and Techniques
Volume65
Issue number12
Early online date4 Oct 2017
DOIs
Publication statusPublished - 1 Dec 2017

Bibliographical note

provisional acceptance date added, based on publication information

Keywords

  • MMICs
  • Baseband
  • Radar tracking
  • Bandwidth
  • Phase modulation
  • Long Term Evolution

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