TY - JOUR

T1 - Conditions of half-frequency oscillation in high-power amplifier with FET and its suppression method using quarter-wavelength open-circuited stub

AU - Uchida, Hiromitsu

AU - Itoh, Yasushi

AU - Miyazaki, Moriyasu

AU - Urasaki, Shuji

PY - 2002/6

Y1 - 2002/6

N2 - 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.

AB - 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.

KW - Amplifier

KW - FET

KW - Fourier series analysis

KW - Half-frequency wave

KW - Oscillation

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U2 - 10.1002/ecjb.10008

DO - 10.1002/ecjb.10008

M3 - Article

AN - SCOPUS:0036610892

SN - 8756-663X

VL - 85

SP - 11

EP - 19

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

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

IS - 6

ER -