Conditions of half-frequency oscillation in high-power amplifier with FET and its suppression method using quarter-wavelength open-circuited stub

Hiromitsu Uchida*, Yasushi Itoh, Moriyasu Miyazaki, Shuji Urasaki

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

With regard to the half-frequency oscillation observed in the nonlinear operation of a microwave power amplifier based on FETs, the voltage and current of the FET in a large-signal mode at an excitation frequency of 2f0 are expanded as Fourier series in half this frequency, that is, f0. Then, the condition that the Fourier coefficient for the f0 component is nonzero, namely, the condition of half-frequency oscillation, is derived. It is shown that the half-frequency oscillation takes place when the determinant is zero for the matrix defined by the fundamental excitation components and time averages of the gate-to-source capacitance, mutual conductance, and drain conductance, as well as the load impedance condition at frequency f0. Also, a method for suppression of the half-frequency oscillation by connecting an open stub one-quarter wavelength long at the half-frequency to the output side of the FET is proposed, and its effectiveness is confirmed by experiment.

Original languageEnglish
Pages (from-to)11-19
Number of pages9
JournalElectronics and Communications in Japan, Part II: Electronics (English translation of Denshi Tsushin Gakkai Ronbunshi)
Volume85
Issue number6
DOIs
Publication statusPublished - 2002 Jun
Externally publishedYes

Keywords

  • Amplifier
  • FET
  • Fourier series analysis
  • Half-frequency wave
  • Oscillation

ASJC Scopus subject areas

  • General Physics and Astronomy
  • Computer Networks and Communications
  • Electrical and Electronic Engineering

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