Analysis and elimination of hysteresis and noisy precursors in power amplifiers

Sanggeun Jeon, Almudena Suárez, David B. Rutledge

Research output: Contribution to journalArticlepeer-review

33 Citations (Scopus)


Power amplifiers (PAs) often exhibit instabilities leading to frequency division by two or oscillations at incommensurate frequencies. This undesired behavior can be detected through a large-signal stability analysis of the solution. However, other commonly observed phenomena are still difficult to predict and eliminate. In this paper, the anomalous behavior observed in a Class-E PA is analyzed in detail. It involves hysteresis in the power-transfer curve, oscillation, and noisy precursors. The precursors are pronounced bumps in the power spectrum due to noise amplification under a small stability margin. The correction of the amplifier performance has required the development of a new technique for the elimination of the hysteresis. Instead of a trial-and-error procedure, this technique, of general application to circuit design, makes use of bifurcation concepts to suppress the hysteresis phenomenon through a single simulation on harmonic-balance software. Another objective has been the investigation of the circuit characteristics that make the noisy precursors observable in practical circuits and a technique has been derived for their elimination from the amplifier output spectrum. All the different techniques have been experimentally validated.

Original languageEnglish
Pages (from-to)1096-1106
Number of pages11
JournalIEEE Transactions on Microwave Theory and Techniques
Issue number3
Publication statusPublished - 2006 Mar
Externally publishedYes

Bibliographical note

Funding Information:
Manuscript received June 20, 2005; revised October 14, 2005. This work was supported by the Lee Center for Advanced Networking, California Institute of Technology and by Qualcomm. S. Jeon and D. B. Rutledge are with the Department of Electrical Engineering, California Institute of Technology, Pasadena, CA 91125 USA (e-mail:; A. Suárez is with the Communications Engineering Department, University of Cantabria, 39005 Santander, Spain (e-mail: Digital Object Identifier 10.1109/TMTT.2005.864125


  • Bifurcation
  • Class-E amplifier
  • Hysteresis
  • Noisy precursor
  • Stability
  • Synchronization

ASJC Scopus subject areas

  • Radiation
  • Condensed Matter Physics
  • Electrical and Electronic Engineering


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