Predicting Electromagnetic Fields with GEMACS and the

CEM Framework

Edgar L. CoffeyApplied Research Associates, Inc.

bcoffey@ara.com

Ground Vehicle Antenna Radiation

Center-fed at 50 Watts

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

Start with the Vehicle

Main Menu• Edit• Add Element to Scene• Geometry

Select geometry file

Set rendering features

Set position at origin

Add the Ground Plane

Main Menu• Edit• Add Element to Scene• Ground plane

Select geometry fileSet conductivity = 0.005Set rendering size = 100 m

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)

Request Surface Currents

Main Menu• Edit• Add Element to Scene• Surface/Wire Currents

Value = 73.38 + j0 voltsSelect Results File

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.)

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

Post-Process GEMACS’ Data

The Framework’s Component View tool easily generates requested observables

Generating Surface Currents

Use Component View to post-process data, then view with SmartView

Visualizing Surface Currents

(Currents are color-coded according to their intensity.)

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.

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

Generating IsoSurface ContoursThis map generates two surface and combines them with the vehicle

Visualizing IsoContour Surfaces

5 V/m surface

2 V/m surface

(Front of contours removed for clarity)

Using Light to Enhance the View

(Previous figure viewed from below)

Combining Contours with IsoSurfaces (color mapped)

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