Multi-Spectral THz Micro-Doppler Radar Based on a Silicon-Based Picosecond Pulse Radiator

In this paper, THz vibrometry using a custom picosecond pulse radiator is demonstrated. THz vibrometry is based on the micro-Doppler phenomenon, in which the periodic movement of radar targets modulates the frequency of the electromagnetic waves reflected from their surface. The modulation depth depends on the amount of surface displacement and the carrier frequency. Since the micro-Doppler effect is stronger at higher frequencies, vibrometry in THz band benefits from higher sensitivity compared to RF and mm-wave. In this experiment, sound vibrations with the frequency ranging from 100 Hz to 1 kHz were used to modulate THz carrier tones produced by a broadband THz pulse radiating silicon chip. A music track, a chirp sound, and multiple frequency tones were produced by a speaker, and then were recovered by the downconversion of the modulated THz tone and analog demodulation at the receiver. Additionally, a phase-noise reduction technique is introduced to boost the sensitivity of low-frequency micro-Doppler detection.