Averaging and cancellation effect of high-order nonlinearity of a power amplifier

Chien-Ping Lee, Wenlong Ma, Nanlei Larry Wang

Research output: Contribution to journalArticle

15 Scopus citations

Abstract

Nonlinear distortion of a power amplifier (PA) due to the nonlinear input-output transfer function is studied. The high-order nonlinearity or Fourier components of the output, due to the mixing of input signals, are found to be related to an average integral related to the transfer function, thus giving insight to the cancellation effect of the nonlinearity. A simple formula has been derived to relate the nth-order Fourier component of a nonlinear transfer function with a sinusoidal input to an average integral of the nth-order derivative of the transfer function. The large signal nonlinear distortion of the nth-order can therefore be regarded as a weighted average of the nth-order derivative of the transfer function. For PAs, the averaging effect gives rise to local minima in the intermodulation distortion terms during power sweep because of the cancellation of the positive part and the negative part of the derivative during averaging. We have applied the formula to InGaP heterojunction bipolar transistors PAs and are able to explain most of the observed nonlinear phenomena of the amplifiers.
Original languageEnglish
Pages (from-to)2733-2740
Number of pages8
JournalIEEE Transactions on Circuits and Systems I: Regular Papers
Volume54
Issue number12
DOIs
StatePublished - Dec 2007

Keywords

  • Fourier transforms; heterojunction bipolar transistors (HBT); intermodulation distortion (IMD); nonlinear distortion; power amplifiers (PAs)

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