Data processing: structural design – modeling – simulation – and em – Electrical analog simulator – Of physical phenomenon
Patent
1998-05-29
2000-12-19
Teska, Kevin J.
Data processing: structural design, modeling, simulation, and em
Electrical analog simulator
Of physical phenomenon
703 4, 703 13, G06G 748, G06G 756, G06F 1750
Patent
active
061637629
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to the manufacture of three dimensional planar electric circuits, and more particularly to a method and apparatus for determining the characteristics of the circuits at high frequencies by the use of sub-sectional electromagnetic analysis.
The characteristics of three dimensional planar electronic circuits at high frequencies are important both for fabricating microwave circuits, such as micro strip wave guides and the like that are used in the generation, transmission and reception of microwave signals. High frequency electromagnetic characteristics are also increasingly important in digital circuits that operate at ever higher frequencies. Digital circuits operating in a range of 500 mH are common today, and even higher operating frequencies are expected to be common in the future.
2. Description of the Related Art Including Information Disclosed Under 37 C.F.R. .sctn..sctn. 1.97, and 1.98
One method for analyzing arbitrary planar circuits is described by Rautio and Harrington in "An Electromagnetic Time-Harmonic Analysis of Shielded Micro Strip Circuits", IEEE Transactions of Microwave Theory and Techniques, Vol., MTT-35, No. 8, August 1987. The circuit metallization is divided into small rectangular sub-sections. We will refer to this dividing as meshing. An explicit surface current distribution is assumed to exist in each subsection. The tangential electric field created by the current in each subsection are determined and the magnitude of the current in all subsections is adjusted, so that the weighted residual of the total tangential electric field goes to zero. The surface currents are then determined, and the electromagnetic characteristics of the circuit are known therefrom.
While meshing a circuit into arbitrarily small rectangles can produce any desired degree of accuracy, the step of adjusting the magnitude of the current in each subsection involves inversion of a matrix whose size increases as the square of the number of subsections. Analysis time becomes expensive, and eventually, the time taken to make the analysis is so long that the desired degree of accuracy cannot be obtained.
There is a need for a method and apparatus for determining the electromagnetic characteristics of 3D planar circuits that permits a greater degree of accuracy to be obtained in a reasonable time than has heretofore been possible. In order to reduce the time needed to characterize the circuit, fewer subsections must be used to represent the circuit. The time required to invert a non-sparse matrix increases with the cube of the number of subsections. In addition, if the dimensions of the subsection are halved, the area of the subsection is one-fourth the size of the original subsection and four times the number of subsections are required to cover the same area. The resulting matrix inversion takes 64 times longer.
This invention greatly increases the accuracy with which the amplitude of the current on a subsection can be determined, by utilizing a new meshing technique that we call conformal meshing. Conformal meshing selects basis functions such that an accurate representation of the actual current distribution in a circuit can be realized with a much smaller number of subsections than has been heretofore possible. Conformal meshing permits a circuit to be analyzed with an error that heretofore would correspond only to meshing with a very small subsize, while maintaining the speed normally seen when using a large cell size.
One method for reducing the number of rectangular subsections is to combine rectangular subsections with triangular subsections. Triangles are used to smooth out stair case edges produced with rectangular subsections. Also, merged rectangles have been used in regions where current changes slowly. More specifically, currents are normally high at the edges of planar circuits at high frequencies, and much lower in the centers of such circuits. By using narrow subsections at the edges to represent the high edge
REFERENCES:
Kosanovich et al.; "Modeling of Discontinuities in Microwave and Millemeter Wave Integrated Circuits using the Curvilinear Finite Difference Time Domain Approach"; IEEE MTT-S Inten. Microwave Symp.; pp. 741-744, Jun. 1993.
Kashiwa et al.; "Analysis of Microstrip Antennas an a Curved Surface using the Conformal Grids FD-TD Method"; IEEE Antennas and Propagation Symp.; pp. 34-37, Jul. 1993.
Holland; "Pitfalls of Staircase Meshing"; IEEE Trans. Electro-Comp.; pp. 434-439, Nov. 1993.
Allen W. Glisson/Donald R. Wilton, Simple and Efficient Numerical Methods for Problems of Electromagnetic Radiation and Scattering from Surfaces, IEEE Transactions on Antennas and Propagation, Sep. 1980, vol. AP-28, No. 5.
James C. Rautio/Roger F. Harrington, An Electromagnetic Time-Harmonic Analysis of Shielded Microstrip Circuits, IEEE Transactions on Microwave Theory and Techniques, Aug. 1987, vol. MTT-35 No. 8.
Jones Hugh
Salai, Esq. Stephen B.
Shaw, Esq. Brian B.
Sonnet Software, Inc.
Teska Kevin J.
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