The Capacitances and Surface Charge Distributions of a Shielded Unbalanced Pair (Short Papers)

The capacitance matrix of an unbalanced shielded pair cable is determined theoretically. The wires of the cable are asymmetrically located about the axis of the shield and have different radii; however, the axes of the wires are restricted to lie on a line passing through the axis of the shield. The elements of the capacitance matrix are determined as particular elements of the inverse of a truncated intinite matrix, which relates the Fourier coefficients of the surface charge densities on the inner conductors and the shield to the applied voltage excitations on the cable conductors. The capacitances and surface charge distributions are evaluated numerically for a shielded pair cable, which, due to inaccuracies in the cable manufacturing processes, has one wire with a smaller or larger radius than the other wire of the pair and/or has one wire closer to or farther from the axis of the shield than the other wire of the pair.     

Improved Approximations for the Fringing and Shielded Slab-Line Capacitances

Given the dimensions w/(b - t) and t/b for the slab-line geometry or the dimensions s/b and t/b for the fringing capacitance geometry, it is shown how the capacitances associated with each geometry can be determined accurately from new explicit expressions rather than by a computerized search. The two expansions for the nome q', in terms of the dimensions, which are essential for the calculations, are identical except for signs. Finally, comparisons are made with values of the capacitances obtained by a computerized search.     

The Computation of Coaxial Line Step Capacitances

Accurate values of coaxial line step capacitances have been computed by the method of 'mode matching' at the plane of the discontinuity in a coaxial line, as described by Whinnery, Jamieson, and Robbins in 1944. The capacitances are given in tables, graphs, and as empirical explicit expressions, suitable for programming in digital computers.     

Equivalent Capacitances for Microstrip Gaps and Steps

The excess charge density distribution near gaps and steps in microstrip transmission lines is calculated by the solution of singular integral equations. Data are presented for gaps in microstrips of width-to-substrate-thickness ratios of 0.5, 1.0, and 2.0 and relative dielectric constants ranging from 1.0 to 15.0. For steps in a microstrip line results are given for width-to-thickness ratio of unity, relative dielectric constants of 1.0 and 9.6, while the change of width-to-height ratio is from 0.1 to 10.0. The excess charges are calculated explicitly in relatively short computing times, and the results are believed to be accurate to within a few percent.     

The Filling Factor of Shielded Dielectric Resonators

The use of dielectric resonators at microwave frequencies usually requires a shield to prevent loss of energy by radiation, and a coupling network. The efficiency of a given circuit depends on the filling factor, which expresses the circuit ability to store most of the input energy in the resonator, and little in the coupling network and surrounding space. The resonator is sometimes excited by means of a coupling loop inside the shield, or with a propagating waveguide. In any case, some energy is stored outside the dielectric material. A calculation is presented for the internal and external stored energies, for the case of a rectangular dielectric resonator in a rectangular waveguide. Verification was performed by measuring the insertion loss of an acoustic delay line, which illustrates an interesting application of dielectric resonators.     

The Characteristic Impedance of the Shielded Slab Line

The characteristic impedance of the shielded slab line is worked out exactly in terms of elliptic functions. A design graph is given to cover most practical applications.     

铌代钽滤波器辐射导纳和静电容的计算方法

指出了铌代钽滤波器辐射导纳和静电容的计算方法，给出了计算实例。结果表明，二分节后变迹换能器辐射导纳和静电容约等于分节前的１／４。     

Coupling between Open and Shielded Wire Lines over a Ground Plane

Convenient expressions are derived which permit accurate determination of induced interference in open (unshielded) wire and shielded wire (or coaxial) lines due to ac and transient currents. Curves and tables are presented for obtaining key parameters in the calculation of interference. The limitations of the derived expressions are set forth and an example interference problem is solved. Experimental verification of the analysis is presented.     

DOE-Based Extraction of CMP, Active and Via Fill Impact on Capacitances

Chemical-mechanical polishing (CMP), active and via fills have become indispensable aspects of semiconductor manufacturing. CMP fills are used to reduce metal thickness variations due to chemical-mechanical polishing. Via fills are used to improve neighboring via printability and reliability of low-k and ultra low-k dielectrics. Active region fills are used for STI CMP uniformity and stress optimization. Although modern parasitic extraction tools accurately handle grounded fills and regular interconnects, such tools use only rough approximations to assess the capacitance impact of floating fills, such as assuming that floating fills are grounded or that each fill is merged with neighboring ones. To reduce such inaccuracies, we provide a design of experiments (DOE) which complements what is possible with existing extraction tools. Through the proposed DOE set, a design or mask house can generate normalized fill tables to correct for the inaccuracies of existing extraction tools when floating fills are present. Golden interconnect capacitance values can be updated using these normalized fill tables. Our proposed DOE enables extensive analyses of fill impacts on coupling capacitances. We show through 3-D field solver simulations that the assumptions used in extractors result in significant inaccuracies. We present analyses of fill impacts for an example technology and also provide analyses using the normalized fill tables to be used in the extraction flow for three different standard fill algorithms. We also extend our analyses and methodology to via fills and active region fills, which have more recently been introduced into semiconductor design-manufacturing methodologies and for which sufficient understanding is still lacking.     

Microwave Filters of Coupled Lines and Lumped Capacitances (Correspondence)

Two frequency transformations are given which enable microwave filters to be realized with coupled lines and lumped capacitances from a characteristic prototype lumped network to a good approximation. The procedore includes filters originally proposed by Matthaei and CristaI, and enables realizations for large bandwidths. A number of examples demonstrate the efficiency of the procedures.     

The Limiting Value of the Interaction Between Symmetrical Fringing Capacitances (Short Papers)

It is well known that the fringing capacitances determined for rectangular bars between parallel plates interact with each other when w/(b -t)/spl rarr/0. The limit of this interaction as s/spl rarr/0 for fixed w, b, and t is determined for symmetrical odd-mode fringing capacitances. This limit, together with an exact value known from one rectangular section and the known asymptotic value as s/spl rarr/ 0, permits one to estimate the values for all s. The same is true for the interaction of the symmetrical even-mode fringing capacitances, except that their interaction is readily shown to tend to zero as s/spl rarr/0.     

Analysis of Edge-Coupled Shielded Strip and Slabline Structures

A method for the analysis of edge-coupled strip and slabline structures is presented which uses relatively simple algebraic expressions. The described procedure can be used to analyze directional couplers, interdigitated and comb line filters, and any other structures formed by an array of rectangular edge-coupled transmission lines, of arbitrary thickness, situated between two parallel plates. The analysis is complete in that it allows the conversion of the physical dimensions of the structure into a set of admittance parameters which completely describes its electrical behavior, including both conductor and dielectric losses.     

屏蔽人体模型对电磁波吸收的数值模拟研究

本文用时域有限差分法计算了三类电磁特性不同的材料屏蔽下三层无限长椭圆柱人体模型对电磁波的吸收。结果表明 ,功率密度相同 ,频率在 0 .2～ 6GHz之间的平面电磁波照射下 ,模型吸收的能量、能量在体内的分布及两者对入射电磁波频率的敏感程度严重地受到外加屏蔽的影响。考察了屏蔽材料的电磁特性与其屏蔽效能之间的关系。三类材料的比较显示 ,对人体电磁辐射防护 ,耗散材料优于非耗散材料 ,导电材料优于非导电材料。     

Scattering of a Shielded Surface Wave by a Wall-Impedance Discontinuity (Correspondence)

The Wiener-Hopf technique is used to compute the transmission and reflection coefficients of a shielded surface wave in a parallel-plate waveguide consisting of inductively reactive guiding surfaces and characterized by an abrupt wall-reactance discontinuity.     

应用CMoL进行屏蔽微带圆盘谐振器的全波分析

本文应用圆柱坐标系中直线法原理,在圆柱坐标系中沿径向离散,利用变型的边界条件,推出适合于微带圆盘及圆环谐振器的计算公式和方法,并就微带圆盘谐振器进行数值说教计算,与用其它方法进行的计算结果和实验数据相比较,准确性令人满意。     

A New Fast and Accurate Algorithm for the Computation of Microstrip Capacitances

A new algorithm is presented for the calculation of TEM parameters of microstrips, based on a lumped-circuit model of the microstrip transverse static field. The use of such an algorithm allows one to obtain either very high accuracies or very low computer times when ordinary accuracies are tolerated. Compared with the similar technique by Lennartsson, the analysis method presented here allows substantial reduction in computer time, storage, and errors.     

“三角面对”的后向散射场计算及其应用

本文提出“三角面对”的新概念.并分析了其后向散射场:应用“三角面对”.可非常简单、方便地计算出各种典型的二面角角反射体的后向散射场.     

Shielding Performance of Triply Shielded Coaxial Cables

We determine the shielding effectiveness of a triply shielded coaxial cable and compare it to the performance of a singly shielded cable. Then we apply well-known transmission-line theory to make a parametric study of the shielding performance as a function of the geometrical and electrical parameters of the braids. We suppose that the three braids are homogeneous, in order to use exact expressions relating the transfer impedance to the shield characteristics. We study the influence of the intersheath space on screening effectiveness and on the intersheath resonances. To damp these resonances, a material having a low conductivity could be used between the braids. To improve the shielding at low frequencies, an intermediate copper braid can be replaced by a ferromagnetic material. We take into account the variation of the permeability as a function of frequency and we point out, in this case, the effect of the intersheath space.     

广州雨滴尺寸分布

本文主要介绍利用激光雨滴谱仪在广州开展的雨滴尺寸分布测量结果。按照降雨率的数值大小，将雨分为暴雨、广延雨和小雨三类，分别给出所属雨类的雨滴尺寸的实测分布和拟合分曲线，并将拟合分布曲线和Ｌ－Ｐ、Ｍ－Ｐ，Ｊｏｓｓ分布曲线进行了对比分析。     

屏蔽室接地线对屏蔽效能和信号泄漏的影响

文章主要介绍屏蔽室的接地问题,通过大量实验得出以下结论:①单点接地的屏蔽效能优于多点接地。②接地电阻大小对屏蔽室屏蔽效能没有影响。③接地线的长短对屏蔽效能影响不明显,而对信号泄漏有影响。④屏蔽接地线比裸露接地线信号泄漏小。