Hilbert transform spectrometer using shunted SIS junctions

A millimeter-wave spectrometer using the Hilbert transformation of the resistively-shunted SIS junction response has been designed, fabricated and experimentally studied. The SIS junctions have been used as a Josephson sensor placed in the center of complementary logarithmic spiral antenna. The response was studied in 75-150 GHz frequency band. The resolution below 1 GHz and noise equivalent power about 10¿13-10¿14 W has been measured for the 0.7 ¿ junction. The measured spectrum has been obtained by means of the Hilbert transformation via novel deconvolution program based on the maximum likelihood approach. This allows to diminish the measured interval of bias voltage and to avoid contribution of the noisy part of response curve without loss of the spectral resolution.