A dc SQUID based low-noise 4 GHz amplifier

The de SQUID based RF amplifier (SQA) looks very attractive as an IF amplifier for integration with a SIS mixer and a flex-flow oscillator (FFO) in a fully superconducting submillimeter wave receiver suitable For space applications, Important advantages of the SQA are its sow noise, extremely low power consumption, and complete compatibility with the fabrication process currently used for SIS mixers, Single stage amplifiers with a novel signal coupling circuit has been developed and tested in the frequency range 3,6-4,1 GHz, The I mu m(2) area Nb-AlOx-Nb junctions shunted by Ti resistors are grouped in a double washer de SQUID. Two samples with slightly different designs showed the following gain, noise temperature and 3 dB bandwidth: 10.0+/-1 dB, 5.0+/-1.5 K, 3.86-3.90 GHz, and 6.8+/-1 dB, 22+/-7 K, 3.89-4.05 GHz, respectively.