Superconducting microstrip amplifiers with sub-Kelvin noise temperature near 4 GHz

M. P. Defeo, B. L.T. Plourde

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


We present measurements of an amplifier operating at 3.8 GHz with 150 MHz of bandwidth based on the microstrip input-coil resonance of a dc superconducting quantum interference device (SQUID) with submicron Josephson junctions. The noise temperature is measured using two methods: comparing the signal-to-noise ratio of the system with and without the SQUID in the amplifier chain, and using a modified Y-factor technique where calibrated narrowband noise is mixed up to the SQUID amplifier operating frequency. With the SQUID cooled to 0.35 K, we observe a minimum system noise temperature of 0.55 ± 0.13 K, dominated by the contribution from the SQUID amplifier.

Original languageEnglish (US)
Article number052603
JournalApplied Physics Letters
Issue number5
StatePublished - Jul 30 2012

ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)


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