Photonic Stepped-Frequency Intensity Modulated Comb Terahertz Radar

Abstract

This work presents an ultra-high repetition rate (UHRR) terahertz time-domain spectroscopy (THz-TDS) system with a unique capability – it functions as a close-range pulsed radar with micrometer precision and an unambiguous range (UR) of about 3 mm. To extend the UR, a stepped-frequency intensity modulated comb (s-FIMC) is introduced. This results in a hybrid radar system, where s-FIMC is employed to determine the distance to a target, while the THz-TDS signal is utilized to monitor changes in the target's position with micrometer precision. With a 10 GHz modulation bandwidth, a resolution of 15 mm, and a range accuracy of $\pm$1.47 mm are achieved in s-FIMC mode. In the TDS mode, a range accuracy of $\pm$15 $\rm {\mu }$m is demonstrated.