Dependence of Noise Temperature of Superconducting HEB Mixers on Frequency and Bath Temperature

A log-spiral antenna coupled 0.1-1.5 THz NbN superconducting HEB mixer has been characterized by measuring its double sideband (DSB) receiver noise temperature (T
_rec
) from 0.22 THz to 1.44 THz and at 4 K-7 K bath temperatures. The measured uncorrected T
_rec
is 800 K, 800 K, 750 K and 850 K at 0.22 THz, 0.55 THz, 0.85 THz and 1.44 THz respectively. The optimal bias voltage seems independent to the frequency and bath temperature. The bath-temperature dependence of noise temperature has also been investigated, the bath temperature has limited effect on the noise temperature when it is operated below its transition temperature. A similar frequency response of corrected mixer noise temperature has been observed at 4 K and 7 K bath temperature, which indicates the RF coupling efficiency of planar spiral antenna of HEB mixer.