开关电源印刷电路板电磁兼容问题的研究

印刷线路间的串扰问题是影响开关电源传导干扰水平的主要因素之一,而旨在降低串扰水平的布线设计却一直是设计中难点。本文提出了一种基于电场分析的开关电源印刷电路板EMC辅助设计的思想方法,其基本思想是以干扰强度分布图为参考选择布线区域,以耦合系数的实时计算结果为指导及时调整布线设计,帮助工程师在印刷线路板的设计阶段就把潜在的干扰抑制在尽可能低的水平上。计算和实验的结果证实了这种思想的可行性。     

Waveguide Filter for Reducing Crosstalk in All Optical Networks

A novel filter structure which can reduce the crosstalk in cross-connection and switching in all optical networks based on dense wavelength division multiplexing(DWDM) is presented.The filter is constructed by dielectric waveguide with the waveguide boundary or the waveguide itself uncontinuous in transmitting direction.Using the concept of effective refractive index of plane waveguide system, we can get a special index profile along the wave propagation direction by alternatively changing the thickness of waveguide film or its refractive index.Having proved this kind of waveguides with filtering properties, the design principle of an example is given, which will be very useful to reduce the crosstalk in optical cross-connection and switching in all optical networks based on DWDM. This kind of filters can be easily connected with other related component.     

高性能价格比的1×7混合棒塑料光纤耦合器的研究

提出了使用圆柱形混合棒的 1× 7塑料光纤耦合器 ,它直接使用粗塑料光纤制作混合棒 ,省略了加工难度大、成本高的混合棒拉锥过程 ,因而生产成本较低 ,但也带来了结构性的通道串音。研究了混合棒失配面外接U形光纤光吸收器以降低结构性通道串音的方法 ,制作了实验样品并进行了性能测量。测量结果表明 ,该耦合器的通道串音 <- 4 0dB ,其耦合效率与 1× 7圆锥形混合棒塑料光纤耦合器相同 ,附加损耗可以降至 1.7dB以下 ,该耦合器是一种高性能价格比的塑料光纤耦合器     

数字电路封装的串扰测试方法研究

梳理了数字电路封装串扰测试方法的发展历史，总结了串扰的影响因素。基于对业界串扰测试方法的分析，比较了各种方法间的区别和优缺点，分析了美军标MIL-STD-883K中串扰测试方法很少修订却长期存在的原因。明确了美军标及其他串扰测试方法的适用范围，提出了我国相应标准制修订方向的建议。测试结果表明，标准中的现有方法在评估串扰对整体电路影响方面手段有欠缺，需要结合电磁仿真对串扰影响做出整体评估，并利用实际测试对仿真结果进行校准，从而提高模拟的准确度，此方法可以在我国相应标准的制修订中加以采用。     

Hardness of crosstalk minimization in two-layer channel routing

Crosstalk minimization is one of the most important aspects of high-performance VLSI circuit design. With the advancement of fabrication technology, devices and interconnecting wires are being placed in close vicinity, and circuits are operating at higher frequencies. This results in crosstalk between adjacent wire segments. In this paper, it has been shown that the crosstalk minimization problem in the reserved two-layer Manhattan routing model is NP-complete, even if channels are free from all vertical constraints. It has also been demonstrated that it is hard to approximate the crosstalk minimization problem. Besides, the issue of minimizing bottleneck crosstalk has been introduced that is a new problem for crosstalk minimization. It has been proven that this problem is also NP-complete. It has been further shown that all these results hold even if doglegging is allowed.     

平行传输线间串扰的仿真及分析

在高速电路设计中,信号完整性问题越来越突出,已经成为高速电路设计师不可避免的问题。该文重点研究了平行传输线间的串扰问题,通过信号完整性分析软件Hyperlynx建立了三线串扰模型并进行仿真分析,最后提出高速PCB设计中减小串扰噪声的策略。     

Sophisticated mobile robot sonar sensing with pseudo-random codes

Conventional time-of-flight sonar sensing is widely used within the autonomous mobile robot research community. One of its most severe problems is known as crosstalk. This paper presents experimental results of a new approach which allows one to operate a set of sonar sensors simultaneously. Nevertheless, frequent misreadings caused by crosstalk or external ultrasound sources are eliminated. This is achieved by carefully designing the emitted bursts, i.e. by using appropriate pseudo-random sequences together with a matched filter receiver well known from radar applications.     

FH1915低本底液体闪烁计数器

本文介绍专为测量低水平样品而设计的带有反符合屏蔽的双管符合型液体闪烁计数器。装置对5ml~(14)C标准源的测量效率为76.3％,对5ml糖炭溶液的测量效率为76.8％,本底为0.40±0.02计数/min,优值为14550。对20ml~8H标准源的测量效率为52.6％,本底为1.11+0.02计数/min,优值为2492。测量氚水样时,采用TritonX-100乳化剂直接测水,18ml样品中含有6ml氚水,测量效率为21％,本底为0.68±0.02计数/min,1000min的灵敏度为2.7Tu。     

Perceptual attributes of crosstalk in 3D images

Nowadays, crosstalk is probably one of the most annoying distortions in 3D displays. So far, display designers still have a relative lack of knowledge about the relevant subjective attributes of crosstalk and how they are combined in an overall 3D viewing experience model. The aim of the current experiment is to investigate three perceptually important attributes influencing the overall viewing experience: perceived image distortion, perceived depth, and visual strain. The stimulus material used in this experiment consisted of two natural scenes varying in depth (0, 4, and 12 cm camera base distance) and crosstalk level (0, 5, 10, and 15%). Subjects rated the attributes according to the ITU BT.500–10 in a controlled experiment. Results show that image distortion ratings show a clear increase with increasing crosstalk and increasing camera base distance. Especially higher crosstalk levels are more visible at larger camera base distances. Ratings of visual strain and perceived depth only increase with increasing camera base distance and remain constant with increasing crosstalk (at least until 15% crosstalk).     

多导体线束内串扰概率分布的预测

串扰是电气、电子系统内部多导体传输线间的相互电磁干扰,受其影响系统可靠性往往较差。电缆线束作为典型的多导体传输线,其串扰问题显得尤为突出。针对电缆线束内导线位置的不确定性,提出一种线束内串扰概率分布的预测方法,在假定线束横截面固定的条件下,将线束分为N段,计算单一子段的电磁参数分布律,并利用卷积算法求得整个线束的电磁参数概率分布;基于蒙特卡洛法,结合多导线传输线理论得到线束串扰的概率分布,进而帮助设计者发现系统内潜在的串扰问题、评估遭受串扰影响的系统可靠性。为了得到卷积算法中分段数N的合适取值,以线束的扭绞程度为依据,提出了相应的经验公式,并结合实际算例进行测量。实验结果表明,线束的分段数N应与线束的扭绞程度相适应;线束的扭绞程度越高,线束内串扰的概率分布越集中,有趋于"平均化"的规律。