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On using the shot noise in SIS tunnel junctions for characterizing IF amplifiers

Authors:
David Woody, Steve Padin, Henry LeDuc, Jeff Stern
Abstract:
The IF amplifier in SIS heterodyne mixers can represent a major contribution to the receiver noise. Achieving quantum limited performance of SIS receivers will require accurate measurement and characterization of this noise contribution. A standard method for in situ characterization of the IF amplifier uses the shot noise from the SIS tunnel junction biased above the gap voltage as a calibrated noise source. This provides an accurate measurement of the IF amplifier noise and gain for source impedances equal to the normal state resistance of the junction, Rn. This paper describes an extension of this technique to determine the 2-port noise and gain parameters of the IF amplifier by using the junction as a noise source over its full dc bias range. Measuring the IF output power over the full bias range (with no LO applied) samples the IF amplifier response for source impedances ranging from zero to > 10Rn . The IF amplifier characteristics are obtained by fitting the measurements to a six parameter model of the IF amplifier system. Although there is insufficient data to accurately determine the standard noise and gain parameters, the contribution from the IF system to the receiver noise is accurately determined.
Categories:
SIS Receivers
Year:
1995
Session:
2
Full-text:
Download a PDF of this paper.
Page Number(s):
140-149