噪声系数（NoiseFigure，NF）是超导混频器的一个重要参数，是衡量超导混频器内部噪声、影响混频器灵敏度的一个重要指标．实验基于小型脉冲管制冷系统，搭建高温超导约瑟夫森双晶结混频器噪声系数自动测量系统，工作温度为60K．Ar离子刻蚀工艺技术制备高温超导YBa2Cu3O7-8（YBCO）／MgO约瑟夫森双晶结，通过y-因子噪声测量法，测量YBCO／MgO约瑟夫森双晶结混频器的噪声系数．实验成功制备了特征电压约1mV的YBCO／MgO约瑟夫森双晶结，在650GHz信号辐照下，有明显的夏皮罗（Shapiro）台阶．在210GHz信号辐照下，进行30次谐波混频，约瑟夫森双晶结在不同偏置电压点中频输出信噪比变化范围约为30dB．在77K与300K不同输入噪声功率下，测得双晶结混频器噪声系数最小值为10dB，偏置电压在300μV
Noise figure (NF) is an important parameter of the superconducting mixer, which is a key indicator of the mixer's sensitivity depending on the internal noise. Using the efficient and durable small size pulse tube refrigerator for the cold source, we designed the High Temperature Superconducting (HTS) Josephson junction harmonic mixer and noise figure automatic measurement systems which operated at 60 K. YBazCu30T-s (YBCO)/MgO Jo- sephson junctions was fabricated through argon ion band etching. Using the Y-factor measurement method, we esti- mated the noise figure of the HTS Josephson junction mixer with conventional hot/cold blackbodies irradiation techniques. The Josephson junction, we had successfully fabricated, had lmV characteristic voltage, and it had good microwave response and high harmonic numbers at operating frequencies around 650 GHz. At the 30th harmonic of fs 210GHz, the double-crystal Josephson junction biased in the different voltages, IF output signal to noise ratio changed in the range of 30 dB. tion of blackbodies at 77 K and 300 K.
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