共查询到20条相似文献,搜索用时 15 毫秒
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提出了超导约瑟夫森结模型(并联电阻—电容结模型),给出了约瑟夫森效应的一些重要结果。在分析约瑟夫森结电路方程时,研究了其中出现的混沌特性和子台阶现象。计算获得的结果对混沌数字通信和超导电子学的应用将起到重要作用。 相似文献
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采用PSpice电路仿真的方法,研究了结电容C较小的情况下,电阻电容并联约瑟夫森结模型的参数(临界电流Ic和正常态电阻Rn)对Shapiro台阶高度的影响.发现在射频电流较大的情况下减小Rn可以提高台阶的高度,而在射频电流较小的情况下增加Rn可以提高台阶的高度.保持Rn不变,取不同Ic绘制的台阶高度-射频电流幅度曲线表明,临界电流越大,曲线所对应的台阶高度也越大.研究结果对利用约瑟夫森结作为电压标准和THz信号检测具有指导意义. 相似文献
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S. A. Guz I. G. Ruzavin M. V. Sviridov 《Journal of Infrared, Millimeter and Terahertz Waves》2000,21(2):285-298
The stochastic dynamics of the Josephson junction is studied when external noise is nonwhite and high-pass filtered (“green” noise). In this case the diffusion coefficient of the Fokker-Planck equation is zero. Therefore the phase locking between the wave functions of the Cooper pairs is described and interpreted by the Krylov-Bogoljubov averaging method. The maximum (“critical”) Josephson current is redefined. Nonlinear diffusion and the lifetime of the phase locking of wave functions are considered. Background illumination, zero-point fluctuations and filtered white noise are used as examples of green noise. It is shown that the effect of green noise on the superconducting state of the junction is much less destructive than that of white one. 相似文献
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为方便约瑟夫森结及其相关电路的仿真研究,根据约瑟夫森方程首次提出了约瑟夫森结的电路模型,给出了具体的电路原理图,并进行了封装.利用这个模型可以对约瑟夫森结的相关特性进行深入系统的仿真研究,这样不必自己编写程序对系统的微分方程进行数值求解,大大提高了工作效率.利用这个模型,对约瑟夫森结的混沌行为、相位锁定特性、RSFQ电路和SQUID进行了研究,结果说明了模型的正确性和实用性,模型的建立对于促进超导器件的相关研究具有一定意义. 相似文献
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为实现高性能处理器,超导RSFQ(快速单磁通量子)电路被提出.该电路主要由超导约瑟夫森结和超导无源传输线组成,对其建模分析是超导RSFQ电路设计的基础.本文提出了基于FDTD(时域有限差分)的约瑟夫森结与超导传输线的协同分析方法.该方法采用FDTD数值方法求解超导传输线的电报方程.在超导传输线与约瑟夫森结交界处的非线性边界条件上,采用了Newton-Raphson迭代算法.数值结果表明,本文提出的约瑟夫森结和超导传输线的协同分析方法与WRspice仿真软件相比具有相同精度,且运算效率显著提高. 相似文献
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《Microwave Theory and Techniques》1976,24(11):706-709
A new method to produce permanent Josephson junctions for millimeter-wave mixers is reported. In contrast to conventional point contacts which are mechanically unstable and require adjustments after each cooldown, these point contact junctions are set at room temperature, stay mechanically stable, and can be temperature cycled without readjustments. Using these junctions in a modified Sharpless wafer mixer mount, a single-sideband noise temperature of 71 K was measured at 47 GHz. Based on these results, system noise temperatures of less than 100 K are predicted for practical broad-band radiometers, RADAR, and communications receivers up to at least 100 GHz 相似文献
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通过三维电磁仿真技术设计并制作了8mm波段Fabry-Perot谐振腔,并建立起一套Fabry-Perot谐振腔高温超导约瑟夫森结特性测试系统.用它测量了Tl2Ba2CaCu2O8(Tl-2212)高温超导薄膜双晶约瑟夫森结的毫米波辐照特性,得到高质量的夏皮罗台阶,并与在U形波导测试系统中测得的结果进行了比较,发现利用Fabry-Perot谐振腔测量技术可显著提高外加电磁场与约瑟夫森结的耦合效率,为进一步研究毫米/亚毫米波信号检测、THz波信号源等研究打下坚实的基础. 相似文献
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Adaptive echo cancellation is being used on shorter telephone circuits. However, while echo cancelers do tend to be effective on the shorter circuits, a new (and undesirable) phenomena called bursting has been observed. Bursting is characterized by long periods of successful echo attenuation alternating with short periods of wildly oscillating signals. The authors studied bursting by constructing a pair of simplified models of adaptive hybrid systems. The models are analyzed when they are excited by various DC and sinusoidal inputs, and the results are related back to the systems of interest, providing insight into the fundamental sources of the bursting problem-an imbalance of excitation and the enclosure of an adaptive filter in a feedback loop. Simulations providing corroborating evidence are discussed 相似文献
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The least mean square (LMS) algorithm is known to converge in the mean and in the mean square. However, during short time periods, the error sequence can blow up and cause severe disturbances, especially for non-Gaussian processes. The paper discusses potential short time unstable behavior of the LMS algorithm for spherically invariant random processes (SIRP) like Gaussian, Laplacian, and K0. The result of this investigation is that the probability for bursting decreases with the step size. However, since a smaller step size also causes a slower convergence rate, one has to choose a tradeoff between convergence speed and the frequence of bursting 相似文献
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Fiske steps which are normally present in the I-V curve of Josephson junctions disappear if the junction is subjected to a magnetic field which reverses its direction at the center of the device as in Josephson fluxonic diode. Experimental results for small and long Josephson junctions are provided. It is proposed that the reversing magnetic field sets extra conditions at the center of the junction which makes the creation of standing electromagnetic waves impossible. 相似文献
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Leonardo Maria Reyneri 《Analog Integrated Circuits and Signal Processing》2002,30(2):101-119
This tutorial paper presents an annotated overview of existing hardware implementations of Artificial Neural Systems based on Pulse Stream modulations, including also Spiking Neurons. Pulse Streams are quasi-periodic binary waveforms which convey analog information on waveform timing.The theoretical bases of Pulse Stream computation and multiplexing are shown for all the existing techniques. Pulse Stream modulations and multiplexing are then analyzed in terms of accuracy, response time, and both power and energy requirements. The performances of the various techniques are compared both with each other, and with those of other analog computing systems. 相似文献
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Uchida A. Iida H. Maki N. Osawa M. Yoshimori S. 《Applied Superconductivity, IEEE Transactions on》2004,14(4):2064-2070
We numerically demonstrate the generation of chaos in a four-terminal superconductive device made of five Josephson weak-link junctions, which is referred to as "Josephson tetrode," for the applications of ultrafast random signal generations at frequencies of hundreds of gigahertz. In the Josephson tetrode, two junctions are series-connected and three junctions are parallel-connected. We calculate the dynamics of electrical voltages across the junctions when one of the normal resistances is varied. We confirm the generation of chaos by using a bifurcation diagram, three-dimensional attractors, and the Poincare sections. The bifurcation diagram can be interpreted as the quasi-periodicity-breakdown scenario to chaos. We clarify that the mechanism of the generation of chaos is a nonlinear frequency mixing among three independent voltages across the junctions. The condition of the generation of chaos can be predicted from the values of the coefficients in the equations of our model. 相似文献
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《Electron Devices, IEEE Transactions on》1980,27(10):1870-1882
Operating principles and criteria for the design of Josephson memory cells are reviewed and the evolution of cell design is retraced to highlight the various constraints imposed by the requirement for high speed, density, large Operating margins, and ease of auxiliary memory circuit design. Two attractive cells have emerged so far. One is a nondestructive readout (NDRO) ring cell for a subnanosecond cache memory chip; the other a destructive readout (DRO) single-flux quantum cell for main memory applications. Both are presently being used as the basis for ongoing design work. 相似文献
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《Microwave Theory and Techniques》1980,28(5):490-500
A review of the progress in the field of Josephson digital devices and circuits is presented. Since the first report of measurements on the switching speed of a Josephson junction in 1966, a large variety of circuits have been developed, with one having a delay of only 13 ps. With miniaturization beyond the present 2.5-mu m linewidths, this remarkable speed probably can be exceeded. It is pointed out that the high speed is combined with very low power so that the high packing density needed to make use of the speed is possible. The paper reviews the Josephson junction and its incorporation into logic gates and memory cells. References are given to larger systems using these elements. 相似文献
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Przybysz J.X. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1989,77(8):1274-1279
A review of Josephson shift-register circuits that have been designed, fabricated, or tested is presented with emphasis on work in the 1980s. Operating speed is most important, since it often limits system performance. Older designs used square-wave clocks, but most modern designs use offset sine waves, with either two or three phases. Operating margins and gate bias uniformity are key concerns. The fastest measured Josephson shift register operated at 2.3 GHz, which compares well with a GaAs shift register that consumes 250 times more power. The difficulties of high-speed testing have prevented many Josephson shift registers from being operated at their highest speeds. Computer simulations suggest that 30-GHz operation is possible with current Nb/Al 2O3/Nb technology. Junctions with critical current densities near 10 kA/cm2 would make 100-GHz shift registers feasible 相似文献
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The status of the superconductive Josephson technology is presented with emphasis on the activities related to the digital systems area. The important properties of the Josephson tehnology which make it potentially the highest performance technology are briefly, reviewed. After an introduction to the Josephson junction and devices, the system components such as logic, memory, and package are discussed. The chip fabrication process is reviewed and some experimental chips are described. 相似文献