Investigation on 600-GHz-Band FMCW Photonic Radar System for a Flexible Inspection Distance

Abstract

A frequency modulated continuous wave (FMCW) photonic radar system in the 600-GHz-band is proposed for flexible-range inspection. The operating frequency is swept from 450 GHz to 750 GHz within ~48 msec, which corresponds to a range resolution of ~0.8 mm. The linearity of the sweeping laser is calibrated, and the collimated beam is applied for achieving a flexible imaging distance. It is demonstrated that the coating material with a thickness of ~500 µm can be distinguished with the collimated beam and results are validated with the results obtained by the terahertz (THz) time domain spectroscopy. It is also shown that the proposed system has a potential for achieving a flexible imaging distance within ~700 mm, which make it suitable for mounting on robotic platforms for large scale inspection, without using complicated signal processing.