Performance of a 700 GHz unilateral finline sis mixer

Boon Kok Tan, Ghassan Yassin, Paul Grimes, Karl Jacobs, Christopher Groppi

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Scopus citations


We present a novel design and the measured performance for a superconductor-insulator-superconductor (SIS) mixer, operating near the superconducting gap of niobium (Nb), in the frequency range of 600-700 GHz. A key feature of the mixer design is the employment of a unilateral finline taper to provide smooth transition from the high-impedance waveguide mode to the low-impedance of planar circuits suitable for the operation of SIS tunnel junction. This geometry of the transition can be electromagnetically modelled and optimised to give a short mixer chip with wide RF bandwidth. The finline taper and all the superconducting transmission lines are integrated on-chip and deposited on a 60 μm thick quartz substrate. This results in an extremely simple mixer block design, comprising a feed horn and a straight waveguide section; no backshort or any mechanical tuning structure is needed. In this paper, we describe the design of the mixer chip, including full electromagnetic simulations of the passive circuits, combined with the heterodyne mixer gain and noise temperature predictions.We have tested the mixer performance from 595 GHz to 702 GHz and measured best receiver noise temperature of 145 K at 600 GHz, corrected for a beam splitter of 75 μm thickness. The need for a thick beam splitter was caused by the lack of sufficient power from the local oscillator (LO) which was optimised between 630-720 GHz and because our mixer was tuned low as a result of larger than designed tunnel junction. Nevertheless, our investigation has demonstrated that superconducting finline mixers work well at high frequencies and have several advantages over other designs, in particular simple mixer block and large substrate for integration of planar circuits.

Original languageEnglish (US)
Title of host publication22nd International Symposium on Space Terahertz Technology 2011, ISSTT 2011
PublisherInternational Symposium on Space Terahertz Technology
Number of pages4
StatePublished - 2011
Event22nd International Symposium on Space Terahertz Technology 2011, ISSTT 2011 - Tucson, AZ, United States
Duration: Apr 25 2011Apr 28 2011


Other22nd International Symposium on Space Terahertz Technology 2011, ISSTT 2011
Country/TerritoryUnited States
CityTucson, AZ


  • Onchip integration
  • Planar circuit
  • SIS mixers
  • Submillimeter wave receivers

ASJC Scopus subject areas

  • Computer Networks and Communications
  • Space and Planetary Science
  • Electrical and Electronic Engineering
  • Atomic and Molecular Physics, and Optics
  • Radiation


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