A sub-terahertz real aperture imaging radar

Abstract

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].

G-Band FMCW Doppler Radar for Close-Range Environmental Sensing

“…The comparative rarity of these systems is due to the general challenges of working at these frequencies, where system components are expensive and relatively inefficient compared to W-band and below, and where the fundamental issues of low output power and high receiver noise figure are compounded by higher atmospheric absorption. Coherent systems with high chirp or pulse repetition frequencies, capable of measuring both range and significant Doppler velocities, are even rarer still [10], [21], [22], [26], [30], [33]- [36]. The radar presented in this paper is not only Doppler capable, but has a fine range resolution, narrow antenna beam, and good phase noise performance which produces highly detailed measurements of targets and the environment.…”

Generalized Radar Range Equation Applied to the Whole Field Region

“…Therefore, the electromagnetic scattering should not be approximated by the plane wave when the THz radar system detects a target, as shown in Figure 1. In addition, power generation is a fundamental problem for THz radar systems [9,10]. The source of the THz radar emitters is in the watt level, which means most of the THz radar systems can only work in the near-field region.…”