A 110 GHz superconductor insulator superconductor (SIS) tunnel junction receiver has been developed and used in regular astronomical observations on the 4m radio telescope at the Department of Astrophysics, Nagoya University. The SIS junction consists of a sandwich structure of Nb/AlOx/Nb, and is cooled to 4.2K with a closed cycle He-gas refrigerator. The receiver exhibits a best double side band noise temperature of 23±2 K at 110GHz. Additional measurements at 98–115 GHz indicate that the receiver has a good response over this input frequency range.

A 110 GHz SIS receiver for radio astronomy

SIS mixers in which superconducting tuning elements are integrated with the tunnel junctions have resulted in very low noise heterodyne receivers in the range 68–260 GHz. Above ∼120 GHz the need for extremely small reduced-height waveguides is avoided by mounting the SIS junctions in a suspended-stripline circuit coupled to a full-height waveguide by a broadband probe. The special characteristics of coplanar transmission line permit the design of SIS mixers with low parasitic reactances. Such a mixer operates over the full WR-10 band (75–110 GHz) without mechanical tuners.

Some recent developments in the design of SIS mixers

A superconductor-insulator-superconductor (SIS) mixer with a broadband integrated tuning structure is described. The mixer is tunable from 85 to 116 GHz and at 114 GHz has a noise temperature >

An 85-116 GHz SIS receiver using inductively shunted edge junctions

A 110-118-GHz receiver based on a superconducting quasiparticle tunnel junction mixer is described. The single-sideband noise temperature is as low as 68 + or - 3 K. This is nearly twice the sensitivity of any other receiver at this frequency. The receiver was designed using a low-frequency scale model in conjunction with the quantum mixer theory. A scaled version of the receiver for operation at 46 GHz has a single-sideband noise temperature of 55 K. The factors leading to the success of this design are discussed.

Low-noise 115-GHz receiver using superconducting tunnel junctions

The design and fabrication of air-bridged, ultra-low-capacitance Schottky barrier diodes are described. Mott diodes, for mixer applications, and varactor diodes, for use in frequency multipliers, have been produced simultaneously on epitaxial wafers grown by molecular beam epitaxy. Typical mixer diodes have a nominal anode contact area of 4 mu m/sup 2/ and exhibit a total zero-bias capacitance of 4.0-4.5 fF (including a parasitic capacitance of approximately 1.0 fF) and a series resistance of 6-8 Omega . Diode chips have been incorporated in hybrid integrated circuit (MIC) mixers for 33-50 GHz and 75-110 GHz and an MIC frequency tripler for 90-140 GHz. Fully monolithic (MMIC) subharmonically pumped mixers for 75-110 GHz have also been fabricated and tested. >

Low-parasitic, planar Schottky diodes for millimeter-wave integrated circuits

The authors describe an easily fabricated H-plane transformer for use in rectangular waveguide carrying the dominant mode. An approximate theoretical analysis of the structure is presented, and computed results are compared with measurements on transformers at X-band. Design curves are given for transitions from full to one-haff, one-third, and one-quarter height waveguide. The new transformers have been found particularly useful for millimeter-wave mixers and multipliers employing split-block construction. The structure can also be used as a transition from rectangular to channel waveguide.

Design and Analysis of the Channel Waveguide Transformer

The authors describe an easily fabricated H-plane transformer for use in rectangular waveguide carrying the dominant mode. An approximate theoretical analysis of the structure is presented, and computed results are compared with measurements on transformers at X-band. Design curves are given for transitions from full to one-half and one-quarter height waveguide. The new transformers have been found particularly useful for millimeter-wave mixers and multipliers with split-block construction. The structure can also be used as a transition from rectangular to channel waveguide.

D.W. Peterson

Papers

Design and Analysis of the Channel Waveguide Transformer

The Channel Waveguide Transformer: An Easily Fabricated H-Plane Transition for the Rectangular TE-10 Mode