Analysis of High Power Amplifier Instability due to f0/2 Loop Oscillation

Tadashi TAKAGI  Mitsuru MOCHIZUKI  Yukinobu TARUI  Yasushi ITOH  Seiichi TSUJI  Yasuo MITSUI  

IEICE TRANSACTIONS on Electronics   Vol.E78-C    No.8    pp.936-943
Publication Date: 1995/08/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Microwave and Millimeter-Wave Technology)
amplifier,  high power,  instability,  loop oscillation,  analysis,  

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A novel nonlinear analysis method of high power amplifier instability has been developed. This analysis method deals with a loop oscillation in a closed loop circuit and presents the conditions for oscillation under large-signal operation by taking account of mixing effect of FETs. Applying this analysis to the high power amplifier instability that an output power for the fundamental wave (f0-wave) decreases at some compression point where a half of the fundamental wave (f0/2-wave) is observed, it has been found that this instability is caused by an f0/2 loop oscillation. In addition, it has been verified by analysis and experiment that the oscillation can be removed by employing an isolation resistor in a closed loop circuit.