Predicting Electromagnetic Fields with GEMACS and the CEM Framework Edgar L. Coffey Applied Research Associates, Inc.

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 file Set conductivity = Set rendering size = 100 m

Excite the Antenna with 50 Watts Main Menu Edit Add Element to Scene Impressed Source Value = j0 volts Segment No. 16 Frequency = 50 MHz (No load)

Request Surface Currents Main Menu Edit Add Element to Scene Surface/Wire Currents Value = j0 volts Select Results File

Request Near-Zone Electric Fields -40 m < X < 40 m -40 m < Y < 40 m 0 m < Z < 26 m dx = 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 Contours This 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