DC SQUID RF amplifier with external mm-wave pumping and its testing by SIS junction noise

Abstract

The power gain and the noise temperature of a DC SQUID RF amplifier at a signal frequency 400 MHz were measured in the presence of external microwave radiation at 2 cm, 8 mm and 4 mm wavelengths. The authors used a four-loop planar DC SQUID with an integrated input coil and very low values of inductances and stray capacitances. In the noise measurements they used an SIS junction as a precise source of input noise at high DC bias voltage Vb>V2 Delta . In such a configuration the studied system is the same as an SIS mm-wave mixer with a SQUID IF amplifier.