Millimeter-wave diode-grid frequency doubler

Abstract
Abstruct-Monolithic diode grids have been fabricated on 2-cm square gallium-arsenide wafers in a proof-of-principle test of a quasi-optical varactor millimeter wave frequency multiplier array concept. An equivalent circuit model based on a transmission-line analysis of plane wave illumina- tion was applied to predict the array performance. The doubler experi- ments were performed under far-field illumination conditions. This ap proach facilitates detailed comparison between theory and experiment. A second harmonic conversion efficiency of 9.5 percent and output powers of 0.5 W were achieved at 66 CHz when the diode grid was pumped with a pulsed source at 33 GHz. This grid had 760 Schottky barrier varactor diodes. The average series resistance was 27 0, the minimum capacitance was 18 fF at a reverse breakdown voltage of -3 V. The measurements indicate that the diode grid is a feasible device for generating watt-level powers at millimeter frequencies, and that substantial improvement is possible by improving the diode breakdown voltage. The excellent agree- ment between experiment and the predictions of the theoretical model provide confidence in predictions of achievable CW output power levels of 2.5 W at a frequency of 188 CHz with an edge-cooled grid containing loo0 diodes.

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