Monolithic image-rejection optoelectronic up-converters that employ the MMIC process

The authors present very small 30-GHz-band monolithic image-rejection optoelectronic up-converters that employ the HEMT MMIC process for the first time. MMIC HEMT optoelectronic mixers are characterized by their direct photodetection and nonlinear characteristics. It is shown that common-source configurations have higher response than common-drain configurations, and up-converter applications are preferable to down-converter applications based on the HEMT direct photodetection characteristics. These characteristics are used to realize 30-GHz-band monolithic image-rejection optoelectronic up-converters. An in-phase divider and a branch-line hybrid with two HEMT optoelectronic mixers are successfully integrated in an MMIC chip with an area of 1.5 mm×1.1 mm. Fundamental performance is demonstrated and excellent wideband performance, which comes from the well-balanced operation of monolithic integrated circuits, is confirmed. These monolithic optoelectronic mixers can be used to realize compact and cost-effective one-chip optical receivers, for fiber optic links which support millimeter waves