A Low-Noise Terahertz SIS Mixer Incorporating a Waveguide Directional Coupler for LO Injection

• Published in: Journal of infrared, millimeter and terahertz waves Vol. 31; no. 11; pp. 1321 - 1330
• Main Authors: Kojima, Takafumi, Kuroiwa, Kouichi, Uzawa, Yoshinori, Kroug, Matthias, Takeda, Masanori, Fujii, Yasunori, Kaneko, Keiko, Miyachi, Akihira, Wang, Zhen, Ogawa, Hideo
• Format: Journal Article
• Language: English
• Published: Boston Springer US 01.11.2010; Springer Nature B.V
• Subjects: Classical Electrodynamics; Cryogenic temperature; Directional couplers; Electrical Engineering; Electronics and Microelectronics; Engineering; Frequency ranges; Horns; Insertion loss; Instrumentation; Joining; Mixers; Noise; Operating temperature; Radio frequencies; Radio frequency; Radio telescopes; Receivers; SIS (superconductors); Terahertz frequencies; Waveguides; Low noise; Waveguide coupler; Superconductor-Insulator-Superconductor mixer; Atacama Large Millimeter/submillimeter Array
• ISSN: 1866-6892; 1866-6906
• DOI: 10.1007/s10762-010-9699-8

We have developed a low-noise heterodyne waveguide Superconductor-Insulator-Superconductor (SIS) mixer with a novel local oscillator (LO) injection scheme for the Atacama Large Millimeter/submillimeter Array (ALMA) band 10, over the frequency range 0.78–0.95 THz. The SIS mixer uses radio frequency (RF) and LO receiving horns separately and a waveguide 10 dB LO coupler integrated in the mixer block. The insertion loss of the waveguide and coupling factor of the coupler were evaluated at terahertz frequencies at both room and cryogenic temperatures. The double-sideband (DSB) receiver noise temperatures were below 330 K (7.5 hf / k B ) at LO frequencies in the range 0.801–0.945 THz. The minimum temperature was 221 K at 0.873 THz over the intermediate frequency range of 4–12 GHz at an operating temperature of 4 K. This waveguide heterodyne SIS mixer exhibits great potential for practical applications, such as high-frequency receivers of the ALMA.