Investigation of wire grid and surface PATCH modeling using the Numerical Electromagnetics Code (NEC)

The Numerical Electromagnetics Code (NEC) was used to evaluate the admittance and the electric near and far fields of a monopole antenna mounted on a cubical box over a perfectly conducting ground plane. Two models of the box, employing surface patches and wire grids, were evaluated. The monopole was positioned at the center, the edge, and at a corner of the box's top surface. NEC admittance results were obtained and good agreement was found with experimental data and with results from PATCH, another independent electromagnetic modeling code. Results are presented in contour and 3-D formats for the near fields and polar format for the far field radiation patterns using surface patch and wire grid models in NEC. Excellent agreement was obtained for both approaches in NEC after finding the optimum number of patches and wire grid segmentation to obtain convergence. This paper provides guidelines for convergence for both modeling approaches and indicates a six-fold savings in run-time for the surface patch method. Furthermore, results are presented in modern graphical format for near field comparisons of the two NEC techniques.