Due to the lack of high-power sources along with strong electromagnetic absorption by water vapor at frequencies between ~100 GHz and ~10 THz, there are very few radar systems, or any other systems for that matter, operating in this region of the spectrum. For this reason, it is sometimes referred to as the terahertz gap. Source technology, however, is improving, thus facilitating radar systems operating in this new frontier of the electromagnetic spectrum. At the lower end of this spectral region near the millimeter/submillimeter transition, components are more readily available and atmospheric attenuation is moderate in comparison to higher frequencies.Utilizing components that can generate on the order of 50 mW of power, a real aperture radar for imaging surfaces up to several hundred meters has been developed. Transmitting a vertically oriented fan beam to scan the Field of View (FOV) in azimuth and receiving at two vertically, displaced locations with identical fan beams forming an interferometer, three dimensional images of the surface topography (in range, azimuth and height) can be generated. This paper describes the design of the prototype system and presents initial results, expanding on prior work [1].

Due to the paucity of high-power sources along with strong electromagnetic absorption by water vapor at frequencies between ~100 GHz and ~10 THz, there are very few radar systems operating in the terahertz range of the spectrum. Source technology, however, is improving, thus facilitating radar systems operating in this gap. The Near-Millimeter Wave (NMMW) range typically refers to frequencies from 100 to 1000 GHz, or, wavelengths straddling the transition from millimeter to sub-millimeter (3 mm to 300 m). At the lower end of this range where components are more readily available and atmospheric attenuation is moderate an interferometric radar system for imaging surfaces up to several hundred meters has been designed and is being built. By scanning a fan beam and receiving at two displaced locations, three dimensional images of the surface topography (in range, azimuth and height) can be generated. This paper describes the design considerations for this radar and the prototype system.