[11p-S421-1~19] 3.9 Terahertz technologies

[11p-S421-7] Terahertz-Wave Amplitude-Modulated Radar Based on a Resonant-Tunneling-Diode Oscillator

〇Adrian Dobroiu¹, Ryotaka Wakasugi¹, Yusuke Shirakawa¹, Safumi Suzuki¹, Masahiro Asada¹ (1.Tokyo Tech)

Keywords:terahertz, radar, resonant-tunneling diode

We present an amplitude-modulated continuous-wave (AMCW) radar based on a resonant-tunneling-diode (RTD) oscillator emitting at 522 GHz. The output power of the RTD oscillator is modulated by adding a sinusoidal signal to the bias voltage. The terahertz beam is allowed to propagate to the target and the reflected beam is detected. The phase of the detected signal is measured, allowing the propagation distance to be calculated. To remove the ambiguity caused by the sine wave periodicity, two modulation frequencies are used. A two-step calculation gives an absolute and accurate distance to the target. In this report we improve upon previously published results by completely changing the phase measurement method. Instead of using an oscilloscope, we built a quadrature demodulation setup based on a hybrid coupler and two mixers, which output the sine and the cosine of the phase. With the new method, the distance measurement error dropped from 0.6 mm to 0.12 mm.