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Predicting Electromagnetic Fields with GEMACS and the
CEM Framework
Edgar L. CoffeyApplied Research Associates, Inc.
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Ground Vehicle Antenna Radiation
Center-fed at 50 Watts
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Ground Vehicle Radiation Problem
• Modeling Scenario– Antenna on vehicle over ground plane– Radiates in all directions
• Observables– Find where radiation levels are “excessive”
• Steps– Build an EM model of the scene– Execute GEMACS to find fields– Extract desired observables from raw data– Use SmartView to render the results
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Start with the Vehicle
Main Menu• Edit• Add Element to Scene• Geometry
Select geometry file
Set rendering features
Set position at origin
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Add the Ground Plane
Main Menu• Edit• Add Element to Scene• Ground plane
Select geometry fileSet conductivity = 0.005Set rendering size = 100 m
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Excite the Antenna with 50 Watts
Main Menu• Edit• Add Element to Scene• Impressed Source
Value = 73.38 + j0 voltsSegment No. 16Frequency = 50 MHz(No load)
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Request Surface Currents
Main Menu• Edit• Add Element to Scene• Surface/Wire Currents
Value = 73.38 + j0 voltsSelect Results File
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Request Near-Zone Electric Fields
-40 m < X < 40 m-40 m < Y < 40 m 0 m < Z < 26 mdx = dy = dz = 2 m
(Only a small part of the lattice is shown.)
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Export to GEMACS and Run
(Hand-generated GEMACS input shown for clarity.)
Main Menu• File• Export• GEMACS
Enter file name
Main Menu•Execute•Launch GEMACS 6.11
Field Output Request
Frequency and Excitation
Segment and Conductivity
Results XML File
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Post-Process GEMACS’ Data
The Framework’s Component View tool easily generates requested observables
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Generating Surface Currents
Use Component View to post-process data, then view with SmartView
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Visualizing Surface Currents
(Currents are color-coded according to their intensity.)
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Generating Contour Maps
The full 3D field data set is read into Component View via XMLReader, then the user selects a “cut plane” on which to generate contours. The data are written to a SmartView-compatible file.
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Visualizing Contours of Fields
• Rendered with AE’s SmartView.
• Viewing contours from above.
• Vehicle forward direction is +x axis.
• YZ-plane is vehicle’s front face
• Contour is taken at z = 2 m
• Color scale units are in Volts/meter
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Generating IsoSurface ContoursThis map generates two surface and combines them with the vehicle
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Visualizing IsoContour Surfaces
5 V/m surface
2 V/m surface
(Front of contours removed for clarity)
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Using Light to Enhance the View
(Previous figure viewed from below)
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Combining Contours with IsoSurfaces (color mapped)
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Summary of Ground Vehicle Simulation and Visualization
• Building the scene (15 minutes)
• Predicting fields (25 minutes)
• Post-processing the data (15 minutes)
• Visualization and Screenshots (20 minutes)
• All was done on a laptop PC with GEMACS and the CEM Framework