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Experimental Design Method for HighEfficiency Microwave Power Amplifiers Based on a LowFrequency Active Harmonic LoadPull Technique
Ryo ISHIKAWA Yoichiro TAKAYAMA Kazuhiko HONJO
Publication
IEICE TRANSACTIONS on Electronics
Vol.E99C
No.10
pp.11471155 Publication Date: 2016/10/01
Online ISSN: 17451353
DOI: 10.1587/transele.E99.C.1147
Type of Manuscript: Special Section PAPER (Special Section on Microwave and MillimeterWave Technology) Category: Keyword: high efficiency, power amplifier, active loadpull, harmonic tuning,
Full Text: PDF>>
Summary:
A novel experimental design method based on a lowfrequency active loadpull technique that includes harmonic tuning has been proposed for highefficiency microwave power amplifiers. The intrinsic core component of a transistor with a maximum oscillation frequency of more than several tens of gigahertz can be approximately assumed as the nonlinear current source with no frequency dependence at an operation frequency of several gigahertz. In addition, the reactive parasitic elements in a transistor can be omitted at a frequency of much less than 1GHz. Therefore, the optimum impedance condition including harmonics for obtaining high efficiency in a nonlinear current source can be directly investigated based on a lowfrequency active harmonic loadpull technique in the lowfrequency region. The optimum load condition at the operation frequency for an external load circuit can be estimated by considering the properties of the reactive parasitic elements and the nonlinear current source. For an InGaAs/GaAs pHEMT, active harmonic loadpull considering up to the fifthorder harmonic frequency was experimentally carried out at the fundamental frequency of 20MHz. By using the estimated optimum impedance condition for an equivalent nonlinear current source, highfrequency amplifiers were designed and fabricated at the 1.9GHz, 2.45GHz, and 5.8GHz bands. The fabricated amplifiers exhibited maximum drain efficiency values of 79%, 80%, and 74% at 1.9GHz, 2.47GHz, and 5.78GHz, respectively.

