Abstract
We report on a recent progress on resonant-tunneling-diode (RTD) terahertz oscillators and its radar applications
including three-dimensional imaging. A fundamental oscillation up to 1.98 THz was obtained
by a slot antenna with small conduction loss and a high-power operation of 0.7 mW at 1 THz was
achieved by a large-scale oscillator array. For higher frequency and higher output power, structures with
cavity resonators were proposed. For good uniformity and reduction in fabrication process, structure-
simplified devices were developed. Using the high frequency modulation characteristics of RTD
oscillators, we proposed and developed ranging systems using the RTD oscillators with the amplitude-
modulated continuous-wave (AMCW)，the frequency-modulated continuous-wave (FMCW)，and
the discrete Fourier transform (DFT) radar principles. These radar system shows fine ranging errors of
below 1 mm by optimization in modulation setup and signal processing.
