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噪声系数(Noise Figure,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-δ(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 superconducting mixer and it is an important index to measure the internal noise of the superconducting mixer and affect the sensitivity of the mixer.Experiment is based on the small pulse tube refrigeration system, Conducting Josephson double crystal junction mixer noise figure automatic measurement system, the working temperature is 60K.Ar ion etching process technology preparation of high temperature superconducting YBa2Cu3O7-δ (YBCO) / MgO Josephson twin junction, measured by Y-factor noise Method to measure the noise figure of the YBCO / MgO Josephson bimodal junction mixer.The YBCO / MgO Josephson bimodal junction with a characteristic voltage of about 1 mV was successfully prepared and the obvious shapiro Shapiro) step.Under the 210GHz signal irradiation, 30th harmonic mixing, Josephson twin junction at different bias voltage intermediate frequency output SNR range of about 30dB.In the 77K and 300K different input noise power , Measured double crystal junction mixer noise figure minimum 10dB, bias voltage at 300μV.