Anechoic Chamber Simulation Tool using Integrated FDTD and SBR Ray Tracing

Accurate analysis of electromagnetic anechoic chambers is a challenging problem.The geometry is complicated and includes multiple antenna radiators, targets,supporting structures, and absorber. Furthermore the frequency range isextensive, traversing a broad range from 200 MHz to 18 GHz. For largechambers this means the chamber size in wavelengths varies over a verylarge range over which different calculation methods must be applied forgood accuracy. Our approach is that for the lower range of frequenciesthe finite difference time domain (FDTD) method will be used to analyzethe entire anechoic chamber. At the higher frequencies shooting andbouncing ray methods will be used. At intermediate frequencies theFDTD method can be used to analyze portions of the anechoic chamber,such as feed and target regions, with these results used to excitethe shooting and bouncing ray method in a hybrid fashion. Both methodswill be integrated under a single graphical user interface which willallow operator control of the excitation antennas, target geometry, andcalculation parameters. The GUI will also provide display of fields overa variety of surfaces inside the chamber and straightforward comparisonwith measured fields for validation.The primary anticipated benefit of the proposed anechoic chamber simulationtool will be more accurate and reliable measurements.These will result from the ability to use the simulation tool to planthe test configuration, taking into account the radiation and scatteringfrom the various antennas, support structures, absorber, and thetargets themselves. This will be done prior to the actual measurementsbeing made, so that measurements will not need to be repeated due tounexpected disturbance of the desired illuminating field by the testarticles or other structures in the chamber.