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John P. Wikswo Jr. Nestor G. Sepulveda Yu Pei Ma W. Patrick Henry Daniel J. Staton Duane Crum 《Journal of Nondestructive Evaluation》1993,12(2):109-119
A SQUID magnetometer can be used to measure the magnetic field produced by flaws in a two-dimensional, conducting plate carrying a current. Identification of the flaw-induced magnetic field is difficult because of the large magnetic field associated with the edges of the plate and the current in the leads that connect the plate to the power supply. We have developed a technique by which the wire and edge fields can be cancelled prior to mapping the magnetic field. In this technique, a similar unflawed conducting sheet is placed adjacent to the flawed plate, with a connection between the sheet and the plate at one edge, and with the opposite edges of the sheet and of the plate connected to the two conductors of a coaxial cable. Thus, an applied current will flow along one conductor of the cable, across the cancelling sheet, cross into the flawed plate, return along the plate, and then return to the power supply along the other conductor of the coaxial cable. As a result of this geometry, there is no magnetic field from the lead-in wires because they are coaxial, and the magnetic field due to the edges of the plate is cancelled by the opposing magnetic field of the edges in the adjacent sheet. The extent of cancellation is determined primarily by the separation between the plate and the cancelling sheet, by the thickness of the plate, and by macroscopic inhomogeneities in their electrical conductivities. 相似文献
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Due to technology scaling and increasing clock frequency, problems due to noise effects lead to an increase in design/debugging efforts and a decrease in circuit performance. This paper addresses the problem of efficiently and accurately generating two-vector tests for crosstalk induced effects, such as pulses, signal speedup and slowdown, in digital combinational circuits. These noise effects can propagate through a circuit and create a logic error in a latch or at a primary output. We have developed a mixed-signal test generator, called XGEN, that incorporates classical static values as well as dynamic signals such as transitions and pulses, and timing information such as signal arrival times, rise/fall times, and gate delay. In this paper we first discuss the general framework of the test generation algorithm followed by computational results. Comparison of results with SPICE simulations confirms the accuracy of this approach. 相似文献
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Signature analyzers are very efficient output response compactors for BIST design. The only limitation of signature analysis is the fault coverage reduction (aliasing) due to the information loss inherent to any data compaction. In this article, in order to increase the effectiveness of ROM BIST, we take advantage from the simplicity of the error patterns generated by ROMs and we show that aliasing free signature analysis can be achieved in ROM BIST.This work was performed when the author was on leave from Minsk Radio Engineering Institute, Computer Department, Belorus. 相似文献
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上行链路功率回馈技术(UPBO:upstream power back-off)是VDSL(very high-speed digital subscriber lines)系统中的关键技术,它用于抵消同一电缆中短线对长线引起的严重的远端串扰(FEXT:far-end crosstalk)。文中从功率控制的角度分析了基于迭代注水的自适应UPBO方案,并进行了性能仿真分析。 相似文献
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采用高功率射频信号内部互调失真的包络特性检测与比较技术,对射频功率带外信号进行检测和估计。设计用于高功率射频放大器前馈技术线性化的一个带外信号检测器。探讨如何进行射频载波抵消以及检测放大器互调失真信号。 相似文献