Electrical Characterisation Of Electronic Packages Usinh Method Of Moments And Asymptotic Waveform Evaluation

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Date
2004-03
Authors
Bhathal Singh, Baijit Singh
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Abstract
A complex circuit in an electronic package is generally analyzed using PSPICE ™ - a circuit analysis software tool. However, the interconnecting wires or Printed Circuit Board traces still require a separate modeling - particularly at high frequencies, before they can be used in the package. These transmission lines in a circuit or an electronic package or printing wiring board, meant to transmit signals (either digital or analog) from one point to the other faithfully without any loss of "signal integrity", are often modeled as a system of simple transmission lines whose parameters are extracted using some powerful numerical techniques such as Finite Element Method (FEM) or Method of Moment (MoM). It is critical that, at high frequencies, the system of transmission lines are accurately modeled so that the distortions resulting from crosstalk from neighboring lines and noise from various sources can be accurately predicted, and controlled. The line parameters of interest are usually the self-capacitances, the mutual capacitances, the selfinductances and the mutual inductances for the system of interconnects. The line parameters are so extracted , more often than not, are taken to be constants. And they are used as such in software package like P - SPICE™ for analyzing the circuit. However, of late, attempts have been made to develop a numerical technique that uses Method of Moment (MoM) for modeling the given geometry for the purpose of determining zero-frequency line capacitances and incorporates an Asymptotic Waveform Evaluation (AWE) technique to mode) these capacitances as a function of frequency. We show herein that MoM is a very flexible tool that can model variety of geometries very easily with far less computational effort than, say, FEM - a popular modeling tool. We verify the technique for various geometries such as round conductors, microstrips, stripline and even bent round conductors interconnecting components to a wireboard. We also employ AWE to capture the frequency dependence of the parameters extracted from MoM and verify it for two neighboring microstrip geometry. We show that the computational effort in using AWE is very small compared to brute-force evaluation.
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Printing wiring board , meant to transmit signals
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