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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. 相似文献
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介绍了X波段放大混频组件的研制情况。该组件由限幅器、低噪声放大器、镜像抑制混频器及中频放大器四部分组成。该组件具有噪声系数低、镜频抑制度高、输出功率1dB压缩点大、抗烧毁功率大等特点。 相似文献
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通过超低温实验直接测量了制备的全铌Josephson结的电压源驱动RCSJ模型的I-V特性曲线。建立了Josephson结在电路仿真软件EWB中的模型,极大的方便了Josephson结及相关电路的仿真研究。利用这一新模型对Josephson结的基本特性进行了较为系统的研究,包括RSJ模型和RCSJ模型的直流驱动I-V特性曲线。 相似文献
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报告研究的全是微波超导接收机技术。 报告对约瑟夫逊混频器的工作原理(包括适合解析、计算机研究的数字模型特性和在直流伏安特性中微波产生的严格阶梯公式)进行了分析。在10到15GHz范围内对约瑟夫逊混频作用进行了实验观察,其结果与理论一致。 已经测得了约瑟夫逊混频器的变频损耗,噪声系数和灵敏度。在13GHz时,用点接触可检测的最小信号为-90dbm/MHz(测量的)和-105dbm/MHz(校正的)。 用真空沉积法存低损耗的烧结铝基片上沉积铅,已做成了在10到15GHz范围内工作的小型超导微带谐振器。 在4.2和1.8K时分别测得的空载Q值(14.3GHz)高达200,000和500,000。使用真空沉积法能够同时制做许多插入损耗低、边沿抑制好的小型多元滤波器和预选器。 相似文献
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提出了采用截止波导法与谐波混频法相结合的方式,进行0.14THz高功率短脉冲的频率测量.首先将两个截止频率分别为0.125和0.15THz的非标准矩形波导作为接收端,通过截止波导滤波法获得了太赫兹辐射源的频率范围.然后根据已知的频率范围,将本振频率选择为15—20GHz,则谐波混频的谐波次数确定为8.随后的Ka波段的脉冲测试和0.14THz连续波测试表明,该8次谐波混频器可用于0.14THz脉冲的混频测量.最后,0.14THz脉冲频率测量实验给出了太赫兹辐射源的准确频率为0.1465THz.该方法大大降低了对本振信号的频率要求,且结果准确可信,为长波段太赫兹脉冲的频率测量提供了一种新的思路. 相似文献
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在SrTiO3(STO)基片上制作了Tl-2212双晶约瑟夫森结,并对其进行了微波辐照下的I-V特性测试,观察到了夏皮罗台阶,符合约瑟夫森电压-频率关系.利用数值仿真对约瑟夫森结建立了RCSJ模型,仿真结果与实验数据符合较好,利用此模型深入研究了噪声对结动态特性的影响,解释了噪声影响下结的微波感应台阶幅度减小和极小值展宽现象,提出了有效噪声温度为工作温度和外部噪声的等效温度之和.
关键词:
RCSJ模型
噪声
Tl-2212双晶约瑟夫森结 相似文献
12.
The underdamped Josephson junction subjected to correlated colored noises was investigated. The results indicated that: (i) There
are two critical phenomena in the system; (ii) Net voltage of the system is induced by multiplicative noise, and exhibits
non-monotonic behaviors with noise autocorrelation rate and the Josephson junction capacitance. 相似文献
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Lindell RK Delahaye J Sillanpää MA Heikkilä TT Sonin EB Hakonen PJ 《Physical review letters》2004,93(19):197002
We have investigated the influence of shot noise on the IV curves of a single mesoscopic Josephson junction. We observe a linear enhancement of zero-bias conductance of the Josephson junction with increasing shot-noise power. Moreover, the IV curves become increasingly asymmetric. Our analysis on the asymmetry shows that the Coulomb blockade of Cooper pairs is strongly influenced by the non-Gaussian character of the shot noise. 相似文献
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We consider a two-level system (TLS) with energy level separation plankvOmega0 inside a Josephson junction. The junction is shunted by a resistor R and is voltage V biased. If the TLS modulates the Josephson energy and/or is optically active, it is Rabi driven by the Josephson oscillations in the running phase regime near the resonance 2eV=plankvOmega0. The Rabi oscillations, in turn, translate into oscillations of current and voltage that can be detected in noise measurements. This effect provides an option to fully characterize the TLS inside Josephson junction and to find the TLS's contribution to the decoherence when the junction is used as a qubit. 相似文献
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《中国物理快报》2016,(11)
We consider a superconducting(Josephson) junction driven by the thermal noise with an ac drive current and a dc constant bias current in the overdamped case and in the underdamped case,respectively,and investigate the effect of the constant bias current on the evolution of the net voltage versus the driving frequency.It is shown that,with some suitably selected values of the system's parameters,suitably increasing the absolute value of the constant bias current can lead to the enhancement of resonant activation of the net voltage versus the driving frequency.This result can benefit the investigation for the Josephson junction subjected to the constant bias current(or voltage). 相似文献
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We measure current fluctuations of mesoscopic devices in the quantum regime, when the frequency is of the order of or higher than the applied voltage or temperature. Detection is designed to probe separately the absorption and emission contributions of current fluctuations, i.e. the positive and negative frequencies of the Fourier transformed nonsymmetrized noise correlator. It relies on measuring the quasiparticles photon assisted tunneling current across a superconductor-insulator-superconductor junction (the detector junction) caused by the excess current fluctuations generated by quasiparticles tunneling across a Josephson junction (the source junction). We demonstrate unambiguously that the negative and positive frequency parts of the nonsymmetrized noise correlator are separately detected and that the excess current fluctuations of a voltage biased Josephson junction present a strong asymmetry between emission and absorption. 相似文献
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We discuss the origin of decoherence in Josephson junction qubits. We find that two level systems in the surrounding insulator cannot be the dominant source of noise in small qubits. We argue that electron traps in the Josephson barrier with large Coulomb repulsion would emit noise that agrees both in magnitude and in temperature dependence with experimental data. 相似文献
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M. Tarasov D. Golubev V. Shumeiko Z. Ivanov E. Stepantsov O. Harnak T. Claeson 《JETP Letters》1998,68(5):454-459
An experimental investigation is made of the subharmonic Shapiro steps observed on the I-V curves of high-T
c
superconductor Josephson junctions and on the bias-voltage dependences of the rf noise and detector response when the junctions
are subjected to external submillimeter radiation. Structures of this type are ordinarily described by a nonsinusoidal current-phase
relation, which is why subharmonic steps appear. Numerical modeling of the processes occurring in a Josephson junction by
means of a simple current-phase relation, as in the case of an SNS junction, gives good agreement with experiment. The width
of the characteristic Josephson generation line of the junction was estimated on the basis of the noise dependences and the
selective detector response. The width can be explained by taking into account the shot noise of the tunneling component of
the conductivity. A model of the conductivity of a high-T
c
superconductor Josephson junction, consisting of a tunnel junction with microshorts possessing metallic conductivity, is
discussed.
Pis’ma Zh. éksp. Teor. Fiz. 68, No. 5, 426–430 (10 September 1998) 相似文献
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量子噪声温度计系统可通过比较导体中电子运动的热噪声和量子电压参考噪声精密测量玻尔兹曼常数,其中量子电压噪声源所合成的量子电压参考噪声由一组超导约瑟夫森结阵产生.本文详细介绍了基于Nb/Nb_xSi_(1-x)/Nb约瑟夫森结的量子电压噪声源芯片的设计、制备及测试;采用脉冲驱动模式,合成了具有量子精度的100 kHz交流量子电压信号.结果表明:本文所研制的噪声温度计核心芯片已具备了合成交流电压的功能,可为后续玻尔兹曼常数精密定值、重新定义及复现热力学温度研究提供核心器件. 相似文献