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IEEE Transactions on Terahertz Science and Technology

Modular 2SB SIS Receiver for 600–720 GHz: Performance and Characterization Methods

Andrey V. Khudchenko, Ronald Hesper, Andrey M. Baryshev, J. Barkhof, Fausto Patricio Mena

Published Dec 28, 2016• 10 citations
Publisher

Abstract

A modular sideband-separating (2SB) receiver for 600-720 GHz has been built and tested. The used modular design allows to characterize all the parts separately, including testing of the superconductor-insulator-superconductor (SIS) junctions individually in a double-sideband mode before building them in to the 2SB assembly. The developed 2SB mixer has a single sideband noise temperature below 380 K in the entire operating band and reaches a level of 200 K in the best point. At the same time, the image rejection ratio (IRR) was demonstrated to be better than 11.5 dB over the entire band. However, we have found a discrepancy between the observed and expected performance. To investigate this problem, we have developed and applied methods to characterize RF and intermediate frequency imbalances of a fully assembled 2SB mixer using the SIS junction properties. As result, the IRR of our mixer was found to be limited by the RF imbalance, which is caused by complex standing waves created by reflections from the SIS junctions, the RF hybrid and the RF absorption load.

DOI
10.1109/tthz.2016.2633528

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A modular sideband-separating (2SB) receiver for 600-720 GHz has been built and tested. The used modular design allows to characterize all the parts separately, including testing of the superconductor-insulator-superconductor (SIS) junctions individually in a double-sideband mode before building them in to the 2SB assembly. The developed 2SB mixer has a single sideband noise temperature below 380 K in the entire operating band and reaches a level of 200 K in the best point. At the same time, the image rejection ratio (IRR) was demonstrated to be better than 11.5 dB over the entire band. However, we have found a discrepancy between the observed and expected performance. To investigate this problem, we have developed and applied methods to characterize RF and intermediate frequency imbalances of a fully assembled 2SB mixer using the SIS junction properties. As result, the IRR of our mixer was found to be limited by the RF imbalance, which is caused by complex standing waves created by reflections from the SIS junctions, the RF hybrid and the RF absorption load.
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We have developed a Sideband Separating (2SB) Mixer based on superconductor-insulator-superconductor (SIS) junctions for frequency range 790-950 GHz. In the first test this mixer demonstrated the noise temperature from 450 to 900 K and the image rejection ratio above 15dB in 95% of the band. The SIS mixers used here have DSB noise temperature form 220 to 400 K. These results show that RF waveguide hybrid structure for such a high frequencies can be manufactured with losses level below 0.8 dB. It makes attractive possible ALMA upgrade of Band 10 receivers to 2SB option, because the sensitivity for spectral lines observations can be improved by about 30% by using 2SB mixers instead of DSB ones.
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