THE EMAP1-3 SCALAR FINITE ELEMENT MODELING CODES

EMAP (ElectroMagnetic Analysis Program) is a family of three-dimensional finite element modeling codes that can be used to analyze bounded, 3-dimensional geometries. The EMAP codes are relatively easy to learn to use and are distributed in source code form. EMAP1, EMAP2 and EMAP3 are no longer supported, but they may be useful to educators or researchers who are looking for a basic scalar FEM source code.

The EMAP codes are not intended to compete with commercial finite element modeling codes. They do not have a sophisticated mesh generator, graphical output, or technical support. Their primary strengths are ease-of-use, modest resource requirements, and accurate modeling of simple three-dimensional configurations over a wide range of frequencies.

EMAP1 employs a variational formulation described by Maile [1]. EMAP-2 employs the Galerkin finite element formulation described in papers by Paulsen and Lynch [2,3]. Both EMAP1 and EMAP2 are scalar (node-based) codes. The primary purpose of EMAP1 [4] is to illustrate the "spurious mode" problem, often a problem with scalar full-wave finite element codes. The formulation applied in EMAP2 [5] avoids the problem with spurious modes.

EMAP-3 is a vector (edge element) code. Vector codes are generally not affected by spurious modes and have other inherent advantages. All of the EMAP codes are written in the C programming language and can be compiled and run on PCs, workstations, or mainframes.

USING THE EMAP CODES

After downloading the EMAP source code, it is necessary to compile the program using a compiler appropriate for your own machine. On a unix machine a typical command to compile the source code "emap2.c" and create an executable file called "Emap2" might be:

cc -o Emap2 emap2.c -lm

To run the EMAP code, simply type the name of the executable file followed by the name of the file containing the input. For example:

Emap2 myinput.file

The output will be written to whatever file or files were specified by the output statements in the input file.

EMAP INPUT AND OUTPUT

The EMAP codes analyze structures defined on a rectangular, 3D grid. They all read input stored in the same format, so for example, an input file created for EMAP2 can also be analyzed without modification by EMAP1 and EMAP3. The Standard Input File (SIF) files read by the EMAP codes are relatively easy to generate. In most cases, a simple text editor is all that is needed to create a new input file. For complex geometries, it is possible to create the geometry using a computer aided drawing package and translate the resulting IGES description into a SIF file using the IGES2SIF translation code.

Output from the EMAP codes is in one of two forms. The default output format is simply a listing of each of the elements and their corresponding electric field values. There is also an efield_output keyword that can be used in the input file to specify output files that list the x,y, and z components of the electric field at various points in the configuration.

DOWNLOADS

emap1.c - the source code for EMAP1 (60 kB)

emap2.c - the source code for EMAP2 (60 kB)

emap3.c - the source code for EMAP3 (98 kB)

example1.sif - a sample input file (1 kB)

example2.sif - a sample input file (1 kB)

REFERENCES

[1] G. L. Maile, Three-dimensional analysis of electromagnetic problems by finite element methods, Ph.D. Dissertation, University of Cambridge, U.K., Dec. 1979.

[2] D. R. Lynch and K. D. Paulsen, "Origin of vector parasites in numerical Maxwell solutions," EEE Trans. on Microwave Theory and Techniques, vol. 39, no. 3, pp. 383-394, Mar. 1991.

[3] D. R. Lynch and K. D. Paulsen, "Elimination of vector parasites in finite element Maxwell solutions," IEEE Trans. on Microwave Theory and Techniques, vol. 39, no. 3, pp. 395-404, Mar. 1991.

[4] T. H. Hubing, M. W. Ali, and G. K. Bhat, "EMAP: a 3-D, finite element modeling code for analyzing time-varying electromagnetic fields," Journal of the Applied Computational Electromagnetics Society vol. 8, no. 1, 1993.

[5] T. H. Hubing and M. W. Ali, "EMC Applications of EMAP-2: A 3D Finite Element Modeling Code," Proc. of the 1993 IEEE International EMC Symposium, August, 1993, pp. 279-283.