Simplified modeling of parallel plate resonances on multilayerprinted circuit boards

Multilayer printed circuit boards (PCBs) are currently used in various areas of electronics such as telecommunications. However, high crosstalk between signal vias can cause degradation of performance for these kinds of structures. Resonances of parallel ground or power planes can increase this crosstalk. In this study, a simplified approach to the modeling of these resonances is described. It is assumed that the fields inside the board have characteristically only two-dimensional (2-D) variation. When this hypothesis is valid, it is shown that resonances can be measured on two-layer prototyping boards and simulated using a 2-D finite-difference model. It is additionally noted that a previously suggested method of using coaxial ground vias to suppress coupling between vias is not necessarily effective if there are resonant parallel plates on the board. Agreement between measured and modeled results is good enough for practical design purposes. The main advantages of the method used in this study compared to the more robust three-dimensional (3-D) simulation models are savings in time and costs. Additionally, prototyping is much easier on two than multilayer boards     

Modeling of interconnect capacitance, delay, and crosstalk in VLSI

Increasing complexity in VLSI circuits makes metal interconnection a significant factor affecting circuit performance. In this paper, we first develop new closed-form capacitance formulas for two major structures in VLSI, namely: (1) parallel lines on a plane and (2) wires between two planes, by considering the electrical flux to adjacent wires and to ground separately. We then further derive closed-form solutions for the delay and crosstalk noise. The capacitance models agree well with numerical solutions of three-dimensional (3-D) Poisson equation as well as measurement data. The delay and crosstalk models agree well with SPICE simulations     

高速电路电源/地层间阻抗参数计算与分析

为了快速准确地计算高速电路地层与电源层之间的阻抗参数,基于边界积分方程提出了有效的计算方法.该方法充分利用了实际电源层/地层的结构特征,将三维电磁场问题转化为二维问题,减少了计算时间.由于在计算中不需要考虑整个 电源层/地层结构的格林函数,故该方法可以用于任意边界形状的电路板.基于提出的积分方程法,分析了介质相对电介质...     

Accurate power supply and ground plane pair models [for MCMs]

In this paper, we derive a theory and method for the use of two-dimensional (2-D) discrete transmission lines (TL's) or discrete coupled transmission lines (CTL's) in modeling power supply and ground planes accurately. If the stray coupling between power or local ground and global ground is not significant, the discrete TL's model is used. Otherwise the discrete CTL's model is used. An arbitrarily shaped plane pair is discretized into a 2-D TL or CTL array by an automatic mesh algorithm. The equivalent distributed circuit, including skin loss effect at high frequencies, represents this power ground plane pair. The theory is extended to be applicable to a generic multiple dielectric layer structure. The model computation results are in excellent agreement with S parameter measurements for practical frequency ranges, including the first major resonant nulls and peaks. The null or peak of the S parameter frequency response represents the test port interaction with the resonant standing wave of these planes at that frequency. The resultant S parameter data of these models can be condensed into a simpler N port equivalent circuit to represent a larger hierarchical power and ground plane network for fast simulation     

高速PCB镜像层设计

在高速多层PCB上,镜像层在噪声控制方面起着重要作用.良好的镜像层设计可以降低杂散电感引起的噪声,有助于控制串扰、反射和电磁干扰.本文结合作者的实际设计重点探讨了局部接地层的应用,并通过一个数模混合电路实例给出了一种镜像层分割法以及一些实践中需要注意的问题.     

Potential Solution of a Homogeneous Strip-Line of Finite Width

The exact potential solution for a zero-thickness strip centered between two ground planes of finite width is outlined. For unit separation of the ground planes, the solution is applied to obtain curves of capacitance per unit length for several representative ground plane widths as a function of strip width. The results are valid for all strip widths, including the case in which the strip is wider than the ground planes. The validity of assuming infinite ground plane width is investigated and it is found that such an assumption leads to little error providing the ratio of ground plane width to separation is at least 2.5, and also providing the difference between ground plane and strip width is at least one-half of the ground plane separation.     

Impedance of a transverse slot in the ground plane of an offset stripline

A generalized formulation for the determination of the impedance of a transverse slot in the ground plane of an offset stripline is presented. The results of the analysis are used to compute the variation of slot impedance with strip offset and also with change in position of one of the ground planes. Comparison of the theoretical results with experimental data is presented.     

Coupling between microstrip lines with finite width ground plane embedded in thin-film circuits

Three-dimensional (3-D) interconnects built upon multiple layers of polyimide are required for constructing 3-D circuits on CMOS (low resistivity) Si wafers, GaAs, and ceramic substrates. Thin-film microstrip lines (TFMS) with finite-width ground planes embedded in the polyimide are often used. However, the closely spaced TFMS fines are susceptible to high levels of coupling, which degrades the circuit performance. In this paper, finite-difference time domain (FDTD) analysis and experimental measurements are used to demonstrate that the ground planes must be connected by via holes to reduce coupling in both the forward and backward directions. Furthermore, it is shown that coupled microstrip lines establish a slotline type mode between the two ground planes and a dielectric waveguide type mode, and that the connected via holes recommended here eliminate these two modes.     

Free View Reconstruction of Three-Dimensional Integral Imaging Using Tilted Reconstruction Planes With Locally Nonuniform Magnification

In this paper, we present a method for three-dimensional (3D) free view computational volumetric reconstruction of integral imaging (II) on a tilted reconstruction plane with a locally nonuniform magnification ratio. The reconstruction plane of conventional free view II is parallel to the pickup device. Thus only the part of object parallel to the pickup device can be observed. To overcome this problem, the reconstruction plane could be tilted according to the viewing point by the “One Point Perspective Technique.” A reconstructed 3D image, using tilted reconstruction planes, can have more in-focus surfaces of the 3D object compared to using parallel reconstruction planes. To verify the proposed method, we generate the elemental images of the 3D object, reconstruct 3D images on both parallel and tilted reconstruction planes, and compare the results.      

Effects of ground plane dimensions on patterns radiated by slot antennas

Using a hybrid MoM-UTD formulation, this paper investigates the effects of ground-plane dimensions on the radiation fields of a slot antenna. It is shown that the radiated field strength of a slot cut in a finite ground plane is generally higher than that of a similar slot in a ground plane of infinite extent. Indeed, computational results reveal that the E-plane radiated field strength of a slot is about 3 dB higher when the ratio of the ground plane width to slot length is an even integer; and 1 dB higher when the ratio is an odd integer. In the case of the H-plane, the field strengths radiated by a slot in both infinite and finite sized ground planes are virtually identical, suggesting, therefore, that in this case, the contribution of the edge diffraction is insignificant. Results also indicate that a ground plane thickness of less than 20 mm has negligible effects on the radiation fields, as the strength of coupled fields, which is a manifestation of the effect of the finite thickness of the ground plane, is very small. As a validation, patterns computed compare favourably with experimental data available in the literature.     

Characterization of V-groove coupled microshield line

A new membrane supported air-filled V-groove coupled microshield has been investigated using finite element method. The even- and odd-mode characteristic impedances and the effective dielectric constants have been computed. The dependence on various dimensions has been studied. The crosstalk levels between adjacent lines have been compared with that in coupled microstrip lines, coupled microstrip lines with lateral ground planes, and V-groove structures with and without metallization in the groove.     

Fast fully 3-D image reconstruction in PET using planograms

We present a method of performing fast and accurate three-dimensional (3-D) backprojection using only Fourier transform operations for line-integral data acquired by planar detector arrays in positron emission tomography. This approach is a 3-D extension of the two-dimensional (2-D) linogram technique of Edholm. By using a special choice of parameters to index a line of response (LOR) for a pair of planar detectors, rather than the conventional parameters used to index a LOR for a circular tomograph, all the LORs passing through a point in the field of view (FOV) lie on a 2-D plane in the four-dimensional (4-D) data space. Thus, backprojection of all the LORs passing through a point in the FOV corresponds to integration of a 2-D plane through the 4-D "planogram." The key step is that the integration along a set of parallel 2-D planes through the planogram, that is, backprojection of a plane of points, can be replaced by a 2-D section through the origin of the 4-D Fourier transform of the data. Backprojection can be performed as a sequence of Fourier transform operations, for faster implementation. In addition, we derive the central-section theorem for planogram format data, and also derive a reconstruction filter for both backprojection-filtering and filtered-backprojection reconstruction algorithms. With software-based Fourier transform calculations we provide preliminary comparisons of planogram backprojection to standard 3-D backprojection and demonstrate a reduction in computation time by a factor of approximately 15.     

Effects on signal integrity and radiated emission by split reference plane on high-speed multilayer printed circuit boards

Power/ground partitioning has been used to supply multivoltage levels and to isolate power/ground noise in high-speed multilayer printed circuit boards. However, the partitioning of the power/ground plane breaks the current return path of the signal current through either the power plane or the ground plane, which causes undesired effects such as signal distortion, crosstalk, and radiation. To control and suppress these undesired effects, we should understand the electromagnetic mechanism associated with them. In this paper, the mechanism of the reflection and the transmission of the signal by the slotted power/ground plane is well understood through an analysis of measurements based on time-domain reflectometry. Considering the propagation of a slot wave through the slot line on the power/ground plane, we have successfully explained the changes of the transmitted and reflected waveforms. Furthermore, we have numerically and experimentally investigated the effects of the power/ground partitioning on the radiated emission in various structures. Finally, it is confirmed that the employment of a stitching capacitor on the power/ground slot suppresses the signal distortion and the radiated emission significantly. When the size and the location of the stitching capacitor are designed, there should be a compromise between the noise isolation and the guarantee of the return current path, with considering the resonance frequencies of planes by the capacitor.     

Influence of a floating plane on effective ground plane inductancein multilayer and coplanar packages

The impact of a floating metal layer on the effective ground plane inductance has been investigated in both multilayer (ground planes) and coplanar (ground conductors) packages. For the multilayer case, both thick and thin film geometries were examined, and the results were compared to a thin film coplanar configuration. It was seen that the floating plane actually increases the ground plane inductance in the multilayer case and decreases the ground plane inductance in the lead frame case. Examining the current density in the floating and ground plane and the ground's partial self-inductance and ground-signal partial mutual inductance give a detailed explanation for this phenomenon     

Perceptual strength of 3-D crosstalk in both achromatic and color images in stereoscopic 3-D displays

The cognitive strength of crosstalk in stereoscopic 3-D displays is investigated, and new quantitative analysis methods based on color difference and grayscale levels are developed. Unlike results using existing metrics, results by the new methods agree well with the perceived crosstalk strength in achromatic images with various levels of grayscale. The crosstalk in color images, which has not been studied before, exhibits interesting results in that the crosstalk metric based on the lightness difference expresses the best fit with the perceptual crosstalk when the intended image is black and the chroma value of the counterpart image is large, but the metric using the color difference works better when the intended image is not black. The new metrics reveal that the difference between active and passive 3-D displays is not as large as suggested by conventional crosstalk metrics, and the crosstalk in color images cannot be simply estimated by averaging the crosstalk of red, green, and blue subpixels. The new metrics will be useful in the development of new image processing technology and display technology for better image quality.     

Resonant modes of circular microstrip patches over ground planeswith circular apertures in multilayered substrates containinganisotropic and ferrite materials

In this paper, the authors analyze how the resonant modes of circular microstrip patch resonators are affected by the presence of circular apertures in the ground plane located under the patches. A rigorous full-wave analysis in the Hankel transform domain (HTD) is carried out in order to obtain the resonant frequencies, quality factors, and radiation patterns of the circular microstrip patch resonators over ground planes with circular apertures. With the use of suitable Green's functions in the HTD, the analysis is performed for the case where the circular patches, as well as the ground planes containing the apertures are embedded in a multilayered substrate consisting of isotropic dielectrics, uniaxial anisotropic dielectrics, and/or magnetized ferrites. The numerical results obtained are compared with experimental results, and good agreement is found. The results show that the circular apertures significantly affect the resonant frequencies of circular microstrip patches     

Analysis of crosstalk in HgCdTe p-on-n heterojunction photovoltaic infrared sensing arrays

In this paper, an experimental and theoretical study is carried out of crosstalk between nearest-neighbor devices within a backside-illuminated linear HgCdTe photovoltaic infrared sensing array. The dominant form of crosstalk that occurs in high performance photovoltaic arrays is associated with photogenerated minority carriers that diffuse laterally between adjacent devices within the array. To measure crosstalk, a scanning laser microscope is used to obtain a spatial map of spot-scan photoresponse at a temperature of 80K for individual p-on-n photovoltaic devices within the linear array. These experimental results are compared to calculations performed on a commercial two-dimensional device simulation package. The crosstalk measurements and calculations presented in this paper include results on mid-wavelength infrared planar device structures, as well as long-wavelength infrared mesa-isolated devices, which give measured crosstalk values of 6.2 and 8.3%, respectively. The results indicate that the device simulations are in good agreement with experimental results. Further simulations are carried out to determine the sensitivity of crosstalk to various material and device parameters such as epitaxial layer thickness (7 to 25 μm), illumination wavelength (1.047 to 11.0 μm), minority carrier diffusion length (8 to 90 μm), and diode pitch. It is found that the dominant feature influencing the value of crosstalk is the distance between the region of photogeneration and the collecting p-n junction.     

An experimental study in electrical impedance tomography usingbackprojection reconstruction

This paper reports on experiments designed to evaluate the performance of the equipotentials backprojection method under conditions modeling those of proposed applications of electrical impedance tomography. Small spherical targets were placed inside a saline-filled tank with dimensions similar to a human torso. Data were acquired with a computer-based instrument that applies current to pairs of electrodes located on two horizontal planes and records potential differences between electrodes of a third plane. The relative contrast produced by nonconducting spheres in a uniform saline background was measured on the reconstructed images and used to determine system sensitivity to target volume and to the radial and vertical positions of single spheres. Results show that for radial positions within a critical radius sensitivity is always maximum when the spheres center is on the recording plane and decreases gradually when the target is moved outside this plane. Localization of simple targets in 3-D, with data acquired from multiple recording planes, appears feasible. The results provide guidelines for the interpretation of images with complex 3-D conductivity distributions.     

Capacitance computations in a multilayered dielectric medium usingclosed-form spatial Green's functions

An efficient method to compute the 2-D and 3-D capacitance matrices of multiconductor interconnects in a multilayered dielectric medium is presented. The method is based on an integral equation approach and assumes the quasi-static condition. It is applicable to conductors of arbitrary polygonal shape embedded in a multilayered dielectric medium with possible ground planes on the top or bottom of the dielectric layers. The computation time required to evaluate the space-domain Green's function for the multilayered medium, which involves an infinite summation, has been greatly reduced by obtaining a closed-form expression, which is derived by approximating the Green's function using a finite number of images in the spectral domain. Then the corresponding space-domain Green's functions are obtained using the proper closed-form integrations. In both 2-D and 3-D cases, the unknown surface charge density is represented by pulse basis functions, and the delta testing function (point matching) is used to solve the integral equation. The elements of the resulting matrix are computed using the closed-form formulation, avoiding any numerical integration. The presented method is compared with other published results and showed good agreement. Finally, the equivalent microstrip crossover capacitance is computed to illustrate the use of a combination of 2-D and 3-D Green's functions     

Finite difference modelling of moisture diffusion in printed circuit boards with ground planes

A finite difference model has been applied to diffusion modelling of molecular moisture diffusion in Printed Circuit Boards (PCB) that have ground planes. Capacitance measurements between two ground planes within a PCB during moisture uptake and removal allowed diffusion coefficients to be determined. These diffusion coefficients were then used to look at the effect of ground plane width, hole density and meshed ground plane dimensions on bake time. The effect of plating holes on the bake time has also been investigated. Results show that whilst a few hours are sufficient to bake PCBs with no ground planes, days, or even months are required to remove moisture from within ground planes due to the extra perpendicular distance the moisture must diffuse. The results demonstrate the importance of storage conditions of the PCB, as once moisture has diffused into a board with ground planes; it is often not feasible to remove it.