Compact and Wideband Millimeter-Wave Antenna-Coupled Detector

This paper presents a compact and wideband millimeter-wave antenna-coupled detector, with a Schottky diode directly integrated across the feeding terminals of a planar dipole. An integrated wideband dipole is proposed, as a radiator as well as a radio frequency choke. It contains a pair of folded strips for broadening the bandwidth and a pair of U-slot resonators for sidelobe reduction, both of which facilitate the compact design. To form unidirectional radiation with a low profile, a hybrid reactive impedance surface is presented, which can simultaneously enhance the gain and impedance bandwidths covering the full Ka-band. An equivalent circuit model is provided to illustrate the operating mechanism of this antenna-coupled detector, and the mounting effect caused by the diode is examined. A Ka-band prototype with dimensions of about 1.12 lambda(0) x 1.12 lambda(0) x 0.08 lambda(0) is fabricated and characterized, exhibiting a responsivity between 1500 and 3800 V/W over the full Ka-band. The proposed design has the advantages of broad bandwidth, low profile, small footprint, and mechanically stable structure. It can be fabricated using low-cost printed circuit technology, and can easily be configured into a planar 2-D array, making it suitable for low-cost sensing and imaging applications based on small unmanned aerial vehicles.