Millimeter Wave Imaging with High-Electron-Mobility Transistors

The proposed effort will employ an array of broadband (W band) antennas, integrated with high-speed (subnanosecond) GaN HEMTs in an array, to detect potential threats to military personnel. The system will be low SWaP, low-cost, and will detect a NETD of 3 degrees or less, from at least 15 meters, with a pixel resolution of < 10 cm. Millimeter wave imaging has been shown to be a useful tool in the detection of potential threats to military personnel. Examples include the use of millimeter wave imaging for chemical/biological detection, person-borne improvised explosive device detection, land-mine detection, and unmanned aerial system (UAS) detection. W-band (75 GHz to 110 GHz) imagers have proven to be particularly useful to the military for the detection of these threats. A low-cost solution to imaging in the millimeter wave region has the potential to provide significant benefits to numerous programs within the DoD. High-electron-mobility transistors (HEMTs) and Schottky Diodes have been identified as two technologies with potential for addressing the needs of the Chemical and Biological Defense (CBD) Program through low-cost rectification of signal. Passive direct detection imaging cameras typically consist of an object lens or mirror that projects an image of a scene on an array of radiometers that detect the relative power, forming a planar image similar to that of a standard optical camera. The radiometer pixel outputs are amplified, digitized, and processed to form images of the scene. Recently, InP and GaAs HEMTs have emerged at the cutting edge of radiometry for the W band, harnessing the resonant absorption of radiation by plasma oscillations in the 2DEG (2-dimensional electron gas) comprising the FET active channel. Here, we present an entirely novel approach of GHz detection using COTS GaN HEMTs, but operating in a non-resonant, broadband approach. Nanohmics in collaboration with Prof. Maggie Chen at Texas State University proposes to develop a compact, low-cost W-band imaging system for rapid threat detection. This high-fidelity imager will be designed to provide ≤10 cm resolution from ≥15 m distances with a noise equivalent differential temperature (NEDT) ≤3°C. The use of commercially available transmission lenses and HEMTs with an additively manufactured antenna array gives this solution the potential to provide order of magnitude cost reduction..