Photonic Stepped-Frequency Intensity Modulated Comb Terahertz Radar

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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pm$</tex-math></inline-formula>1.47 mm are achieved in s-FIMC mode. In the TDS mode, a range accuracy of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pm$</tex-math></inline-formula>15 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\rm {\mu }$</tex-math></inline-formula>m is demonstrated.