An Optimum Bias Point Study of Low Local Oscillator Power Operation for 60 GHz Drain Mixer

Keiichi YAMAGUCHI  Yasuhiko KURIYAMA  Eiji TAKAGI  Mitsuo KONNO  

IEICE TRANSACTIONS on Electronics   Vol.E82-C    No.11    pp.1982-1991
Publication Date: 1999/11/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on High-Frequency/High-Speed Devices for Information and Communication Systems in the 21st Century)
Category: Low Power-Consumption RF ICs
drain mixer,  LO power,  bias,  MMIC,  millimeter wave,  

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The optimum bias point for a drain mixer operating on low local oscillator (LO) power was investigated. The bias voltage dependence of the required LO power and the conversion gain in the drain mixer was clarified by a simplified nonlinear model which the drain current characteristics around knee voltage is approximated by two straight line segments. It was found that an optimum gate bias voltage Vgs exists for a given applied LO power, and the optimum gate bias voltage moves toward the pinch-off voltage as the injection LO power level decreases. In order to verify the variation of the optimum gate bias voltage, a 60 GHz MMIC drain mixer adopting the optimum gate bias voltage for low LO power level was fabricated. The fabricated drain mixer exhibited a conversion gain of 0 dB with the injection LO power level of 0 dBm. This value of 0 dBm is the best performance yet obtained for a 60 GHz MMIC drain mixer. The measured optimum gate bias voltage was near the pinch-off voltage. This result was in good agreement with the theoretical analysis. The LO power level of a drain mixer has been improved so that it is on a par with that of a gate mixer.