Frequency down-conversion in self-pumped HTS R-SQUID mixer

A pair of high-temperature-superconducting (HTS) step-edge Josephson junctions connected in the ´resistive-SQUID´ (R-SQUID) configuration has been previously shown to generate a heterodyne oscillation which is frequency-tunable by a control current across the resistor. A method is described which enables the R-SQUID to act both as the local oscillator (LO) and simultaneously as a radio-frequency down-converter element. For the first time the autonomous Josephson mixer-local oscillator device for signal frequencies between 1-5 GHz, over a temperature range of 20-70 K, is demonstrated.