Flux avalanches in a Josephson medium

Avalanche flux penetration dynamics has been experimentally observed in a Josephson medium, a granular high-T _c superconductor, with a slowly increasing external magnetic field. The observed voltage spikes are associated with the stepwise penetration of the field into the superconductor and obey a power-law size distribution. The results directly confirm the hypothesis of self-organized criticality in such a system.     

1/f Flux noise in Josephson phase qubits

We present a new method to measure 1/f noise in Josephson quantum bits (qubits) that yields low-frequency spectra below 1 Hz. A comparison of the noise taken at positive and negative bias of a phase qubit shows the dominant noise source to be flux noise and not junction critical-current noise, with a magnitude similar to that measured previously in other systems. Theoretical calculations show that the level of flux noise is not compatible with the standard model of noise from two-level state defects in the surface oxides of the films.     

Frequency divider by underdamped Josephson transmission line

A parallel array of coupled short Josephson junctions under boundary ac driving is theoretically investigated. The driving response is monitored via numerical simulations on the associated Frenkel-Kontorova model as an oscillating output current at the other boundary junction. The theoretical analysis is conducted assuming the phase locking of boundary driving with exact stationary solution of sine-Gordon equation that can be represented by a kink (fluxon) motion back and forth in the restricted geometry of the array. As a consequence the results suggest the conception of a device which could switch to the conducting regime not according to intensity range but rather to given (quantized) frequency range. Moreover our findings indicate also a frequency converting scenario by choosing appropriately the system length and injected fluxon number.     

非线性传输线中的孤子

分析了波在非线性无色散传输线和非线性有色散传输线中的传播情况,从而引入孤子的概念,分析了孤子的性质,并介绍了有关的实验.     

Flux qubit with a large loop size and tunable Josephson junctions

We present the design of a superconducting flux qubit with a large loop inductance. The large loop inductance is desirable for coupling between qubits. The loop is configured into a gradiometer form that could reduce the interference from environmental magnetic noise. A combined Josephson junction, i.e., a DC-SQUID is used to replace the small Josephson junction in the usual 3-JJ (Josephaon junction) flux qubit, leading to a tunable energy gap by using an independent external flux line. We perform numerical calculations to investigate the dependence of the energy gap on qubit parameters such as junction capacitance, critical current, loop inductance, and the ratio of junction energy between small and large junctions in the flux qubit. We suggest a range of values for the parameters.     

变阻抗传输线能量传输效率分析

采用数值方法分析了阻抗各向同性、波速不变的变阻抗传输线（指数型、双曲型和线性型）的电压反射系数,得到了能量传输效率与归一化频率、阻抗变比之间的关系。结果表明,在低频条件下(归一化频率小于2),指数传输线的能量传输效率最高。计算了Z300装置变阻抗传输线的能量传输线效率,指数线为91.6%、双曲线为90.4%,圆锥线为91.2%。     

变阻抗传输线能量传输效率分析

采用数值方法分析了阻抗各向同性、波速不变的变阻抗传输线（指数型、双曲型和线性型）的电压反射系数,得到了能量传输效率与归一化频率、阻抗变比之间的关系。结果表明,在低频条件下(归一化频率小于2),指数传输线的能量传输效率最高。计算了Z300装置变阻抗传输线的能量传输线效率,指数线为91.6%、双曲线为90.4%,圆锥线为91.2%。     

基于传输线的特异材料

特异材料（metamaterials）是指自然界中不存在的具有奇异电磁特性的人工结构，通常指的是介电常数和磁导率同时为负值的左手材料（left-handed materials）。自从2002年利用传输线制备左手材料的思想被提出后，人们对基于传输线的特异材料进行了大量的研究。文章着重概述了近年来人们所提出的几种典型的传输线特异材料的结构、制备方法、实现左手性的原理以及各自的特点。     

基于传输线的特异材料

特异材料(metamaterials)是指自然界中不存在的具有奇异电磁特性的人工结构,通常指的是介电常数和磁导率同时为负值的左手材料(left\\|handed materials).自从2002年利用传输线制备左手材料的思想被提出后,人们对基于传输线的特异材料进行了大量的研究.文章着重概述了近年来人们所提出的几种典型的传输线特异材料的结构、制备方法、实现左手性的原理以及各自的特点.     

Interference in transmission spectra of overlapping Lorentzian lines

The effect of line overlap on the integrated area between a transmission spectrum and baseline of a system with multiple Lorentzian cross section absorbers has been found to resemble classical optical interference. A generalized analytical expression for the magnitude of the interference effect has been derived and applied to a symmetric doublet system. Results from this particular case illustrate the level of interference with variation of species concentration and ratio of energy separation to line width. In this special case, the interference can be expressed in terms of polynomials based on a phase angle determined solely by the energy separation to linewidth ratio. The coefficients for these polynomial representations of the interference exhibit some interesting mathematical properties and lead to series representations for the symmetric Lorentzian doublet transmission integral and for Mersenne numbers.     

Stochastic broadening of signals in distorsionless transmission lines

The paper presents a theory of a stochastic continuous transmission line in which the series inductanceLΔ[1+l(x)], series resistanceRΔ[1+r(x)], shunt capacitanceCΔ[1+c(x)], and shunt conductanceGΔ[1+g(x)] are defined as Gaussian random functions. (The continuous line is considered as a limiting case of a lumped transmision line.) The non-negative random functionsL(x),R(x),C(x), andG(x) are chosen as delta-correlated, i.e. their correlation function is of the formΘδ(x′ −x″) whereΘ is a 4×4 positive definedx-independent matrix. Propagation of a signal of Gaussian shape is analyzed. A special attention is devoted to the so-called distorsionless lines defined by the deterministic conditionR/L=G/C. As a consequence of the stochasticity of the functionsl(x),r(x),c(x), andg(x), transmitted signals do become distorted: they become broadened. An explicit formula for this broadening is derived. This work has been supported by the Slovak Grant Agency VEGA under contract No. 1/4319/97.     

脉冲功率传输线传输效率的分析与计算

 基于脉冲功率系统磁绝缘传输线的时域仿真结果,分析了磁绝缘建立过程中不同阶段电极间的电子产生的能量损失特性;提出了造成能量损失的因素,包括损失的电子和磁绝缘的电子;给出了影响能量损失大小的因素,包括传输线的线长、半径比和加载脉冲的最大电压、电压的时间变化率等。通过分析不同脉冲功率波形作用下各传输阶段能量损失的起因、大小和影响因素,提出了依据极间的电子分布状态划分传输阶段,及对传输线的总效率分阶段计算的传输效率模型,给出了基于已知的传输效率数值模拟结果对不同阶段的损耗估算并最终估算传输效率的方法。     

脉冲功率传输线传输效率的分析与计算

基于脉冲功率系统磁绝缘传输线的时域仿真结果,分析了磁绝缘建立过程中不同阶段电极间的电子产生的能量损失特性;提出了造成能量损失的因素,包括损失的电子和磁绝缘的电子;给出了影响能量损失大小的因素,包括传输线的线长、半径比和加载脉冲的最大电压、电压的时间变化率等。通过分析不同脉冲功率波形作用下各传输阶段能量损失的起因、大小和影响因素,提出了依据极间的电子分布状态划分传输阶段,及对传输线的总效率分阶段计算的传输效率模型,给出了基于已知的传输效率数值模拟结果对不同阶段的损耗估算并最终估算传输效率的方法。     

Time-domain analysis of lossy coupled transmission lines

A new approach, based on the waveform relaxation technique and fast Walsh transform, is first presented for the analysis of lossy coupled transmission lines (LCTL) with arbitrary terminal networks. The simulation accuracy of the new method can be greatly improved, the disadvantage which always exists in previous methods [1]–[7] can be avoided and a considerable saving in time and memory of CPU is obtained.     

三平板传输线结构的解析分析方法北大核心CSCD

在考虑不等宽度三平板传输线的极板边缘效应和极板厚度的条件下,建立了单位长度电容、特性阻抗和各位置电场强度幅值的解析求解方法。该方法利用保角变换,将三平板传输线的不规则场边界变换为规则边界,所得结果是不带有任何近似的准确值。该方法计算结果与利用商业软件Ansoft进行模拟所得结果一致,证明该方法正确且可行。