THz Sensing & ISAC

Communicating and measuring — as one

The wide bandwidth of terahertz waves is valuable not only for high-capacity communications but also for radar and sensing with high range resolution.

We combine a fast wavelength-tunable laser with photomixing to build THz-FMCW radar that sweeps the terahertz frequency at high speed.

Using a delayed self-multiplexing scheme with a single tunable laser and optical fiber, we generated multiple FMCW waveforms — sawtooth, triangular and dual-chirp — and achieved ranging errors below 1 cm.

We are now extending this work to ISAC (Integrated Sensing and Communication), which performs communication and sensing simultaneously with the same terahertz signal.

Time-domain waveforms and time–frequency analysis of three THz-FMCW waveforms — Multiple types of THz-FMCW waveforms generated with a fast wavelength-tunable laser, and their time–frequency characteristics. Time-domain waveforms of the THz-FMCW signals [(a), (c), (e)] and time–frequency analysis by STFT [(b), (d), (f)]. The LO frequencies after multiplication are 278.4, 279.6 and 279.8 GHz, respectively.

Configuration of the THz-ISAC system — THz-ISAC system using a fast wavelength-tunable laser. FMCW sensing and high-speed data communication are achieved simultaneously with the same 300 GHz-band signal.

Analysis of the FMCW frequency sweep and eye diagrams of the data link — A 9.5 GHz-wide FMCW frequency sweep and data communication at up to 12.5 Gbit/s achieved simultaneously.

Source: R. Kaide et al., “Integrated Sensing and Communication in the Terahertz Band Enabled by Photomixing Using a High-Speed Wavelength Tunable Laser,” International Symposium on Antennas and Propagation (ISAP 2025), 2025.

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