Carrier noise-limited penetration in THz radar imaging

A 675 GHz imaging radar has been developed for standoff personnel screening applications. A key performance metric is the radar's ability to penetrate thick clothing to reveal concealed threats. Here we investigate the limitations of terahertz (THz) radar imaging in the regime of weak penetration, and present evidence that noise carried by the radar signal itself, rather than the receiver's thermal noise floor, is the limiting factor for imaging through thick clothing. This means that higher power sources or lower noise figure receivers at 675 GHz will not improve radar penetration. Rather, efforts in this direction should focus on lowering the THz source's phase noise through better back-end electronics architecture, or operating at lower frequencies at the cost of poorer image resolution.