Development of Supra-THz Schottky Diode Harmonic Mixers

In this paper, we report the development of single-ended, Schottky diode-based harmonic mixers operating at 3.5 THz and 4.7 THz, respectively. Both mixers utilize a sub-micron size Schottky diode fabricated with circuit elements on a suspended 2 µm-thick GaAs stripline circuit, and then assembled in a waveguide split-block. The diode is closely integrated with the RF-waveguide, resulting in an electrically small and compact circuit. For the 3.5-THz, ×6-harmonic mixer, a conversion loss of about 60 dB was measured at an intermediate frequency (IF) of 200 MHz. The predicted mixer performance versus dc bias agrees well with the measurements. Based on these results, the preliminary design and simulation results of a 4.7-THz, ×8-harmonic mixer, are presented.