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一种分析双层多导体微带传输线的有效方法 总被引:1,自引:0,他引:1
本文利用直线法结合周期边界条件,分析了双层多导体微带传输线的色散特性,与直线法结合吸收边界条件的常规方法相比,本文的做法可得到具有解析形式的特征值与特征矢,并且能够利用快速付里叶变换来计算阻抗元素,从而大大提高计算效率.计算实例证明了方法的正确性和有效性.最后给出了几种不同结构微带传输线的色散特性. 相似文献
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时域有限差分法模拟中所用的驻波-行波边界条件(STWBC)具有较高的计算效率,且非常易于实现.但此吸收边界条件最初仅用于直角坐标的情形.文章将STWBC扩展到柱坐标的情形与直角坐标的情形一样,柱坐标中的STWBC也在计算域外附加理想导电(磁)壁进行截断,并将边界处的驻波转化为行波,从而模拟行波在无限大空间的传播.文中给出的数值算例证明了此种吸收边界条件的有效性. 相似文献
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本文推出集总电阻加载圆柱天线在时域有限差分(FD-TD)法中的计算公式,对Mur二阶吸收边界条件在三维FD-TD法计算中的稳定性进行了研究,提出保证Mur二阶吸收边界条件稳定所必须注意的问题。在集总电阻加开圆柱形天线激励下,对色散媒质中三维目标的瞬态电磁散射特性进行了计算和分析,并将部分计算结果与实验测量的结果进行了比较,二者具有比较好的一致性。研究了色散媒质和目标特性艰目标回波信号的影响,并对有 相似文献
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弯曲波导中基于PML边界条件的柱坐标广角BPM 总被引:2,自引:2,他引:0
给出了基于完美匹配层边界条件(PML—BC)的柱坐标广角波束传播方法(BPM)。用(2,2)阶Pade近似的广角BPM对光在弯曲波导中的传输特性进行了计算和分析,获得了比近轴BPM更精确的结果。采用了PML—BC,减小了边界反射,获得了比透明边界条件(TBC)更好的结果。 相似文献
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完全匹配层(PML)吸收边界条件的理论分析 总被引:4,自引:0,他引:4
本文以屏蔽微带线为例,应用谱域方法推导了时域差分(FDTD)法中所用的完全匹配层(PML)吸收边界条件的公式,并且严格证明了有关参数的选择原则.计算表明,在屏蔽微带线中,这种吸收边界条件的反射系数可以小于-80dB.本文所给出的推导方法对于平面分层介质结构是普遍适用的,因为谱域中的每一个波谱实际上都代表一个平面波.文中所给出的推导揭示了这种吸收边界条件的机理,它对于正确使用以及进一步改进这种吸收边界条件都是有意义的. 相似文献
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Direct bonded copper (DBC) substrates have become the most important electronic circuit boards for multichip power semiconductor modules. They are replacing complicated assemblies based on leadframes and refractory metallized substrates due to ease of assembly and the low temperature coefficient of expansion of DBC which matches silicon in spite of thick copper metallization. The DBC technology allows bonding of copper to alumina and aluminum nitride, fusing of copper to copper has been developed to establish efficient water cooling devices with sophisticated internal micro channel structures for cooling power laser diodes and other high power density electronics. Low weight, hermetically sealed DBC packages are replacing more and more heavy weight metal can packages. Increasing requirements for temperature cycling reliability and mechanical stability in automotive, avionics and space applications is the driving force for the development of a new type of DBC material with a 60% increase in flexural strength and more than 100% increase of temperature cycles: This new type of DBC allows 35% thicker copper layers on 20% thinner ceramic, for example 0.4 mm copper on 0.32 mm ceramic. By this the thermal resistance of multichip power modules can be reduced substantially without decreasing reliability. In many applications this will be an economic solution where the price of AlN and Si3N4 substrates would be too high. 相似文献
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《Journal of Visual Communication and Image Representation》2014,25(5):1102-1111
The differential box-counting (DBC) method is one of the frequently used techniques to estimate the fractal dimension (FD) of a 2D gray-level image. This paper presents an improved DBC method based on the original one for improvement of the accuracy. By adopting the modifying box-counting mechanism, shifting box blocks in (x, y) plane and selecting appropriate grid box sizes, it can solve the two kinds of problems which the DBC has: over-counting boxes along z direction and under-counting boxes just at the border of two neighboring box blocks where there is a sharp gray-level abruption exits. The experiments using two sets of synthetic images and one set of real natural texture images demonstrate that the improved DBC method can solve the two kinds of problems perfectly, simultaneously, and can outperform other DBC methods in the accuracy. 相似文献
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一种IEEE 802.16中快速有效的冲突解决算法 总被引:3,自引:0,他引:3
IEEE 802.16宽带无线接入系统在其上行媒体接入控制层采用时,分复用和资源竞争与预留的方式进行接入,各用户站(SS)之间存在着竞争与冲突,这将导致系统性能下降。该文针对SS在碰撞以后的冲突解决过程提出了一种快速有效的冲突解决算法动态退避控制(Dynamical Backoff Control,DBC)算法。在该算法中,基站(BS)通过预测下一个上行帧中将会出现的带宽请求报文数,动态地控制SS的退避范围,以增大每帧中成功发送的带宽请求报文数,从而提高MAC层的数据吞吐,降低SS的平均接入延迟。利用OPNET对DBC和二进制指数退避两种算法进行了仿真。仿真结果显示DBC算法对系统性能有一定的改善和提高。 相似文献
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新型陶瓷/金属化合物基板——直接敷铜板 总被引:4,自引:0,他引:4
直接敷铜(DBC)板是用于电子学封装的一种陶瓷/金属化合物基板。这种DBC板适用于光电子学封装的采集排列制作,并可提供无源对准、好的热导率、CTE匹配及良好的可靠性。本文介绍了采用DBC板的光电子学封概念布线、制作和应用。 相似文献
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A new method to increase circuit functionality and power density per unit area in power electronic modules has been developed. This new method uses the present power hybrids production technology platform on ceramic substrates and implements direct bonded copper (DBC) "partial" multilayer structures on application specific substrates. With this novel approach a more than 50% increased power density and a 40% increased circuit complexity has been achieved. Reliability tests (thermal cycling (TC), power cycling (PC), high temperature reverse bias...) have been performed for several new layout solutions, the most relevant results are shown in this paper. 相似文献
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DBC substrates are the standard circuit boardsfor power modules. Using the DBC technologythick copper foils (0.125mm - 0.Tmm) arecladded to Alumina or Aluminum Nitride,The strong adhesion of the copper to ceramicbond reduces the thermal expansion coefficientin horizontal direction only slightly above theTEC of the ceramic itself. This allows directsilicon attach of large dies without using TECcontrolling layers.As DBC technology is using copper foils,integralleads overhanging the ceramic can be realized... 相似文献
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Yunhui Mei Guo-Quan Lu Xu Chen Chen Gang Shufang Luo Dimeji Ibitayo 《Journal of Electronic Materials》2011,40(10):2119-2125
For many years, direct bonded copper (DBC) substrates have proved to be an excellent solution for electrical isolation and
thermal management of high-power semiconductor modules. However, in this study we detected a copper residue on the surface
of DBC alumina, presumably a result of pattern etching even in industry. As is known, growth of metal dendrites could be observed
with the assistance of electric field, temperature, and humidity. Metal dendrites normally grow from the cathode to anode.
Silver and copper are two kinds of metals susceptible to migration. In this work, copper dendrites could be formed at 400°C
and 50 V/mm between conductors. These dendrites may impact the reliability of DBC in power electronic applications. Therefore,
the formation of copper residue is an interesting phenomenon for etched DBC and warrants further attention in the future. 相似文献