Title :
An Octave Bandwidth SIS Mixer for Accurate and Compact Terahertz Spectrometers
Author :
Kohjiro, Satoshi ; Shi, Sheng-Cai ; Inatani, Junji ; Maezawa, Masaaki ; Uzawa, Yoshinori ; Wang, Zhen ; Shoji, Akira
Author_Institution :
Nat. Inst. of Adv. Ind. Sci. and Technol., Tsukuba
fDate :
6/1/2007 12:00:00 AM
Abstract :
A SIS mixer with RF bandwidth of 1 octave is designed, fabricated, and characterized. The mixer chip consists of 8 Nb/AlOx/Nb junctions connected in parallel through Nb/SiO2/Nb microstrip lines (MSL), a twin-slot antenna, and a 3-stage MSL transformer. Experimentally, the 2.5 dB RF band is found to be 230-440 GHz, which agrees quantitatively with theoretical calculation. Receiver noise temperature Trx is measured as 260-680 K in the band. After correction for IF-amplifler noise and beam-splitter reflectivity, the noise is 170-320 K, i.e., 13-20 times of the quantum noise. The sensitivity flatness in the band can be improved to 1.9 dB by further optimization of the transformer.
Keywords :
mixers (circuits); spectrometers; superconducting devices; 3-stage MSL transformer; AlO - Interface; Nb - Interface; RF bandwidth; SiO2 - Interface; accurate terahertz spectrometers; compact terahertz spectrometers; frequency 230 GHz to 440 GHz; microstrip lines; mixer chip; octave bandwidth SIS mixer; temperature 170 K to 320 K; temperature 260 K to 680 K; twin-slot antenna; Antenna measurements; Bandwidth; Microstrip antennas; Niobium; Noise measurement; Radio frequency; Reflectivity; Spectroscopy; Temperature measurement; Temperature sensors; Heterodyne; SIS mixer; spectroscopy;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
DOI :
10.1109/TASC.2007.898584
