Frequency Multiplier Based on Distributed Superconducting Tunnel Junctions: Theory, Design, and Characterization

In this paper, we present the analysis, design, and characterization of the first frequency multiplier using distributed superconductor-insulator-superconductor (SIS) junctions. We derived analytical expressions describing the properties of the distributed SIS junction as a frequency multiplier. The modeling of the distributed SIS junctions shows that high conversion efficiency can be achieved when used as the multiplier. The measured output power generated by such multiplier employing the distributed SIS junction at the second harmonic of the input frequency is in good agreement with the model. Furthermore, the frequency multiplier based on the distributed SIS junction for the first time was able to pump an SIS mixer. The multiplication efficiency of the distributed SIS junction is 15-30% for a fractional bandwidth of 10% with excellent spectral line purity. The -3 dB line width of the multiplied signal is 1 Hz, which was limited by the resolution bandwidth of the spectrum analyzer. The results attained in this paper show that the distributed SIS junction frequency multiplier has considerable future potential, and could possibly be used in LO source in single-end and multipixel SIS mixer receivers.