Extension of the frequency range of Josephson impedance spectroscopy

The results of the spectral analysis of a high-temperature superconducting (HTSC) log-periodic antenna integrated with a HTSC Josephson junction (JJ) and operating, in this case, as a test resonant system are presented. Current-voltage characteristics of the JJ and dependences of its differential resistance on the voltage across the JJ are measured at a temperature of 5 K by varying the JJ critical current by an external magnetic field in order to extend the operating frequency range of the spectral analysis. The low-frequency boundary of the spectral analysis, which is determined by temperature fluctuations, is lowered to 64 GHz. The equivalent circuit of an integrated device consisting of the JJ and the log-periodic antenna is analyzed. The real part of the antenna admittance is reconstructed from experimental data in the frequency range 65–1200 GHz. Experimental results are compared with the results of numerical calculation.