Title :
Noise properties of HTS Josephson mixers at 345 GHz and operating temperatures at 20 K
Author :
Scherbel, Jens ; Darula, Marian ; Harnack, Oliver ; Siegel, Michael
Author_Institution :
Inst. fur Schicht- und Ionentechnik, Forschungszentrum Julich GmbH, Germany
fDate :
6/1/2002 12:00:00 AM
Abstract :
The authors report on the mixing properties of high-temperature superconductor bicrystal Josephson junctions at 345 GHz and high-operating temperatures. A variable backshort and E-plane tuner enabled the control of impedance matching between the junction and the RF environment. The local oscillator frequency and intermediate frequency were 345 and 1.4 GHz, respectively. The double-side band (DSB) mixer noise temperature and the conversion efficiency were determined using the hot/cold method. The authors observed that the noise temperature was strongly dependent on the matching conditions. The lowest noise temperatures were observed for tuner positions supporting the formation of a subharmonic step which appeared between the zeroth and first Shapiro step. At T = 20 K they obtained a lowest DSB mixer noise temperature of 1003 K and a conversion efficiency of -1.2 dB. They have investigated the dependence of the noise temperature on the operating temperature in detail. The impact of resonances on the device performance will be discussed.
Keywords :
bicrystals; critical currents; high-temperature superconductors; impedance matching; submillimetre wave mixers; superconducting device noise; superconducting junction devices; superconducting microwave devices; superconducting mixers; thermal noise; 20 K; 345 GHz; E-plane tuner; HTSC Josephson mixers; RF environment; Shapiro step; bicrystal Josephson junctions; conversion efficiency; critical currents; double-side band noise temperature; grain-boundary Josephson junctions; high-operating temperatures; hot/cold method; impedance matching; intermediate frequency; local oscillator frequency; noise properties; resonances effect; subharmonic step; submillimeter wave; variable backshort; High temperature superconductors; Impedance matching; Josephson junctions; Local oscillators; Noise shaping; Radio frequency; Superconducting device noise; Temperature dependence; Tuners; Working environment noise;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
DOI :
10.1109/TASC.2002.1020345