Design and characterisation of terahertz Schottky diode harmonic mixers
Licentiate thesis, 2021
First, the influence of idler terminations on harmonic mixer performance and diode embedding impedance at radio and local oscillator frequencies was
studied. Based on this, a 3.5-THz, ×6-harmonic mixer was designed. A planar, single-ended Schottky diode with a sub-µm contact area was realised on a
2-µm suspended GaAs substrate. The integrated mixer circuit was assembled in an E-plane split-block with the aid of beam leads. The Schottky diode anode pad was designed to act as a radio frequency E-plane probe and extended as a beamlead to provide dc ground, resulting in an electrically compact circuit. The design was validated by conducting a sensitivity analysis of critical parameters that are susceptible to fabrication tolerances. Two integrated circuits with Schottky contact areas of 0.11 and 0.14 µm2 were assembled on mixer modules and dc/RF characterisation was carried out. Both harmonic
mixers exhibited a conversion loss of about 60 dB at an intermediate frequency of 200 MHz. When evaluated in a phase-locked loop, it resulted in a
signal-to-noise ratio of 40 dB, which was more than sufficient to phase lock the quantum-cascade lasers.
This work presents uncooled, efficient THz harmonic mixers for stabilising THz optical sources. It opens up many opportunities for building a THz heterodyne spectrometer with a high spectral resolution to detect gas species such as hydroxyl radical and atomic oxygen in the frequency range of 3-5 THz.
RISE Research Institutes of Sweden
Chalmers, Microtechnology and Nanoscience (MC2), Terahertz and Millimetre Wave Laboratory
Effect of idler terminations on the conversion loss for THz Schottky diode harmonic mixers
International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz,; Vol. 2019-September(2019)
Paper in proceeding
A 3.5-THz, x6-Harmonic, Single-Ended Schottky Diode Mixer for Frequency Stabilization of Quantum-Cascade Lasers
IEEE Transactions on Terahertz Science and Technology,; Vol. 11(2021)p. 684-694
Development of Supra-THz Schottky Diode Harmonic Mixers
International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz,; (2021)
Paper in proceeding
THz Schottky diode mixers for high resolution FIR spectroscopy
Swedish National Space Board, 2018-01-01 -- 2019-12-31.
Swedish National Space Board (170/17), 2018-01-01 -- 2019-12-31.
Areas of Advance
Information and Communication Technology
Electrical Engineering, Electronic Engineering, Information Engineering
Chalmers University of Technology
Opponent: Dr. Jeffrey Hesler, CTO, Virginia Diodes Inc. (VDI), USA (Passcode for zoom: 587413)