## 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 2f_{0} are expanded as Fourier series in half this frequency, that is, f_{0}. Then, the condition that the Fourier coefficient for the f_{0} 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 f_{0}. 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 language | English |
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Pages (from-to) | 11-19 |

Number of pages | 9 |

Journal | Electronics and Communications in Japan, Part II: Electronics (English translation of Denshi Tsushin Gakkai Ronbunshi) |

Volume | 85 |

Issue number | 6 |

DOIs | |

Publication status | Published - 2002 Jun |

Externally published | Yes |

## 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