THE EMAP 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.



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 unlimited 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



Executable files for certain Sun, HP, and IBM workstations are located in

the /exe subdirectory.  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 <b>default</b>

output format is simply a listing of each of the elements and their

corresponding electric field values.  There is also an <b>efield_output</b>

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.



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.