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  • 1
    Electronic Resource
    Electronic Resource
    A 691 GHz sis receiver for radio astronomy (1993)
    Springer
    International journal of infrared and millimeter waves 14 (1993), S. 1867-1887 
    Details
    ISSN: 1572-9559
    Keywords: Quasioptical SIS mixers ; submillimeter radiometers ; radio astronomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We report the development of a low noise heterodyne receiver optimized for astronomical observations in the 650 GHz atmospheric window, and specifically for the CO(J=6→5) line at 691.5 GHz. The system is based on an open structure SIS heterodyne mixer pumped by a continuously tunable solid state oscillator. A niobium SIS junction double array is placed at the end of an integrated V-Antenna. For broad band impedance matching a combination of microstrip impedance transformer and radial stub was used. Receiver noise temperatures of 550 K DSB at 684 GHz were achieved at a 1.8 K physical temperature. The performance improved substantially when decreasing the temperature from 4.2 to 1.8 K. Comparison of model calculations and Fourier transform direct detection measurements of the tuning structure implies that this effect is likely due to the coincidence of operational frequency and the gap frequency of the niobium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02096361
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  • 2
    Electronic Resource
    Electronic Resource
    Broadband IF matching for quasioptical mixers (1993)
    Springer
    International journal of infrared and millimeter waves 14 (1993), S. 715-728 
    Details
    ISSN: 1572-9559
    Keywords: Quasioptical mixers ; submillimeter radiometers ; radio astronomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Everyone recognizes the need to drive symmetric quasioptical antennas in a symmetric way to maintain clean antenna patterns; in this note we report on the advantages of bringing out the IF in a symmetric (balanced) way as well. The main difference in IF circuits between waveguide and open structure mixers is that the quasioptical mixers are usually also open at IF wavelengths, so IF currents can flow on the outside of the mixer mounting structures. We measured these surface currents and their associated resonances on a scale model of our mixer block for a 690 GHz SIS mixer. Bringing the IF off the mixer with a balanced circuit solves the surface current problems, yielding a broad bandwidth with predictable impedances. We successfully tested an octave bandwidth IF matching circuit for open structure mixers that incorporates a commercial 180° hybrid at cryogenic temperatures. We also found that surface currents are not significant for corner cube mixers because they generate their own balancing currents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02209277
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    Paper (German National Licenses)
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