Characterization of planar log-periodic antennas at low temperatures using Josephson junctions

Using the Josephson oscillations of high-temperature superconducting (HTS) grain boundary Josephson junctions (GBJJs), we have characterized HTS planar log-periodic antennas from 4.2 K to the critical temperature of the GBJJs. The antennas were designed to operate from 25 GHz to 3.2 THz for a broadband receiver. As a result, several resonant steps were obtained in the dynamic resistance (dY/dI)-voltage (V) curves and the steps can be quite well explained by geometric resonances of the antenna.