Distance measurement using a subcarrier frequency-modulated continuous-wave radar based on a resonant-tunneling-diode oscillator

We introduce a new principle for distance measurement in the terahertz-wave range using a resonant-tunneling-diode (RTD) oscillator as a source at 511 GHz and relying on the frequency-modulated continuous-wave (FMCW) radar technique. Unlike the usual FMCW radar, where the sawtooth frequency modulation is applied to the carrier, we propose applying it to a subcarrier obtained by amplitude modulation; this is advantageous when the source cannot be controlled precisely in oscillation frequency, but can easily be modulated in amplitude, as is the case of the RTD oscillator. The detailed principle and a series of proof-of-concept experimental results are presented.

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Amplitude-modulated continuous-wave radar in the terahertz band using a resonant-tunneling-diode oscillator

2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) ◽

10.1109/irmmw-thz.2019.8874352 ◽

2019 ◽

Author(s):

Adrian Dobroiu ◽

Ryotaka Wakasugi ◽

Yusuke Shirakawa ◽

Safumi Suzuki ◽

Masahiro Asada

Keyword(s):

Resonant Tunneling ◽

Continuous Wave ◽

Resonant Tunneling Diode ◽

Terahertz Band ◽

Tunneling Diode ◽

Wave Radar ◽

Diode Oscillator

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Real-Time Distance Measurement using a Subcarrier FMCW Radar based on a Terahertz-wave Resonant-Tunneling-Diode Oscillator

10.1109/irmmw-thz50926.2021.9567210 ◽

2021 ◽

Author(s):

Jia Ito ◽

Adrian Dobroiu ◽

Safumi Suzuki ◽

Masahiro Asada ◽

Hiroshi Ito

Keyword(s):

Real Time ◽

Resonant Tunneling ◽

Terahertz Wave ◽

Resonant Tunneling Diode ◽

Distance Measurement ◽

Fmcw Radar ◽

Tunneling Diode ◽

Diode Oscillator ◽

Time Distance

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Absolute and Precise Terahertz-Wave Radar Based on an Amplitude-Modulated Resonant-Tunneling-Diode Oscillator

Photonics ◽

10.3390/photonics5040052 ◽

2018 ◽

Vol 5 (4) ◽

pp. 52 ◽

Cited By ~ 12

Author(s):

Adrian Dobroiu ◽

Ryotaka Wakasugi ◽

Yusuke Shirakawa ◽

Safumi Suzuki ◽

Masahiro Asada

Keyword(s):

Resonant Tunneling ◽

Modulation Frequency ◽

Propagation Distance ◽

Sine Wave ◽

Terahertz Wave ◽

Resonant Tunneling Diode ◽

Tunneling Diode ◽

Wave Radar ◽

Diode Oscillator ◽

Modulation Signal

We present the principle of a terahertz-wave radar and its proof-of-concept experimental verification. The radar is based on a 522 GHz resonant-tunneling-diode oscillator, whose terahertz output power can be easily modulated by superimposing the modulation signal on its bias voltage. By using one modulation frequency and measuring the time delay of the returning signal, a relative measurement of the propagation distance is possible; adding a second modulation frequency removes the ambiguity stemming from the periodicity of the modulation sine wave and allows an absolute distance measurement. We verified this measurement method experimentally and obtained a submillimeter precision, as predicted by theory.

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Discrete Fourier Transform Radar in the Terahertz-Wave Range Based on a Resonant-Tunneling-Diode Oscillator

Sensors ◽

10.3390/s21134367 ◽

2021 ◽

Vol 21 (13) ◽

pp. 4367

Author(s):

Hiroki Konno ◽

Adrian Dobroiu ◽

Safumi Suzuki ◽

Masahiro Asada ◽

Hiroshi Ito

Keyword(s):

Resonant Tunneling ◽

Measurement Range ◽

Terahertz Wave ◽

Resonant Tunneling Diode ◽

Swept Source ◽

Tunneling Diode ◽

Wave Radar ◽

Diode Oscillator ◽

Modulation Signal ◽

Wave Range

We used a resonant-tunneling-diode (RTD) oscillator as the source of a terahertz-wave radar based on the principle of the swept-source optical coherence tomography (SS-OCT). Unlike similar reports in the terahertz range, we apply the stepwise frequency modulation to a subcarrier obtained by amplitude modulation instead of tuning the terahertz carrier frequency. Additionally, we replace the usual optical interference with electrical mixing and, by using a quadrature mixer, we can discriminate between negative and positive optical path differences, which doubles the measurement range without increasing the measurement time. To measure the distance to multiple targets simultaneously, the terahertz wave is modulated in amplitude at a series of frequencies; the signal returning from the target is detected and homodyne mixed with the original modulation signal. A series of voltages is obtained; by Fourier transformation the distance to each target is retrieved. Experimental results on one and two targets are shown.

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