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Supercond SIS Rxs at Mm Wavelengths

Mm-wave VLBI Workshop, Shanghai, Nov. 3-4, 2003. Supercond SIS Rxs at Mm Wavelengths. Sheng-Cai Shi Mm & Submm Lab, Purple Mt Observatory, NAOC, China. Mm-wave VLBI Workshop, Shanghai, Nov. 3-4, 2003. OUTLINE. Low noise receiver technologies at mm A 100-GHz SIS mixer on 13.7m

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Supercond SIS Rxs at Mm Wavelengths

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  1. Mm-wave VLBI Workshop, Shanghai, Nov. 3-4, 2003 Supercond SIS Rxs at Mm Wavelengths Sheng-Cai Shi Mm & Submm Lab, Purple Mt Observatory, NAOC, China

  2. Mm-wave VLBI Workshop, Shanghai, Nov. 3-4, 2003 OUTLINE • Low noise receiver technologies at mm • A 100-GHz SIS mixer on 13.7m • Stability of SIS mixers • Summary

  3. Mm-wave VLBI Workshop, Shanghai, Nov. 3-4, 2003 Low Noise Rx Technologies at Mm • Schottky Mixers • HEMT LNAs • Supcond. Mixers

  4. Mm-wave VLBI Workshop, Shanghai, Nov. 3-4, 2003 HEMT LNAs at Mm Wavelengths • cryogenically cooled • InP HEMT devices, available to 190GHz • expensive, noisy & with poor short-term stability over SIS mixers Gain>7dB from 160-190GHz NF=6dB (Te=864K) @ 170GHz

  5. Mm-wave VLBI Workshop, Shanghai, Nov. 3-4, 2003 W-Band Cooled HEMT LNA, NRAO InP HEMT MMIC LNA for JPL by Todd Gaier, Sander Weinreb, Neal Erickson, & Richard Lai freq: 85-115GHz Gain>20dB, 1.4mW power consumption Te=30-107K @ 24K, 250-470K @ room

  6. SIS chip WG Mm-wave VLBI Workshop, Shanghai, Nov. 3-4, 2003 Superconducting SIS Mixers Performance of SIS mixers SIS mixer Junction I-V curve

  7. 半导体Schottky 接收机 CO J=1-0, Orion A 超导SIS 接收机 CO J=1-0, Orion A 馈源 放大器 耦合器 隔离器 SIS 杜瓦 Mm-wave VLBI Workshop, Shanghai, Nov. 3-4, 2003 A 100GHz SIS Mixer 4-K Cryostat Rx Inside Sensitivity ~10 times improved

  8. Mm-wave VLBI Workshop, Shanghai, Nov. 3-4, 2003 Stability of SIS Mixers • DC voltage/current interference • Temperature variation • LO power/LO pumping level variation • PATS with infinite/negative Rdyn • Mechanical vibration

  9. without LO pumping PATS : hn/e=0.414mV DVg Vg=~2.8mV bias point Vg pumping @ 100GHz Mm-wave VLBI Workshop, Shanghai, Nov. 3-4, 2003 DC V/I Interference Temp. Variation • Vg is temp. dependent! • DVg=0.034mV while • DT=0.1K @ 4.2K I-V curve of 100-GHz SIS junction

  10. G C 85-115GHz 2.64 0.4GHz 85-115GHz Att. reference Mm-wave VLBI Workshop, Shanghai, Nov. 3-4, 2003 LO Pumping Level Variation G may varies with telescope position & C changes with G different pumping level C2*PLO! PLO Diagram of a 100-GHz Rx System

  11. 95GHz 90GHz PATS PATS bias point bias point Mm-wave VLBI Workshop, Shanghai, Nov. 3-4, 2003 PATS with Infinite/Negative Rdyn For a constant-I bias while PATS with infinite/negative Rdyn unstable V bias, then unstable PIF!

  12. 95GHz 95GHz Mm-wave VLBI Workshop, Shanghai, Nov. 3-4, 2003 Effect of Magnetic Filed 磁铁 applying B to destroy superconductivity partly smaller Rdyn! To be confirmed! without B with B

  13. Mm-wave VLBI Workshop, Shanghai, Nov. 3-4, 2003 Effect of R in Series with SIS Connecting a resistor in series with the SIS junction have an inclined I-V curve for stable bias!

  14. Mm-wave VLBI Workshop, Shanghai, Nov. 3-4, 2003 Summary • Suppressing AC interference • Stabilizing T (e.g., He-pot) & LO power • Applying B/connecting a R to have smaller Rdyn for stable bias • Constant V bias • Higher-Jc SIS to get rid of the unstable region

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