Investigation of Near Fields for HF Shipboard Antennas - Surface Patch and Wire Grid Modeling Using the Numerical Electromagnetics Code

摘要

The Numerical Electromagnetics Code (NEC) was used to evaluate the admittance, average power gain, and the electric near and far field 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. Admittance and average power gain of the antenna were calculated. NEC result were examined and compared with experimental data and with results from PATCH, another independent electromagnetic modeling code. The near electric field was calculated for both models. Computer graphics technique were presented for plotting NEC near field results using DISSPLA (Display Integrated Software System and Plotting Language), a commercial graphics package. Contour and 3-D amplitude, and phase plots of the near electric fields were presented. Radiation patterns were calculated to relate far field and near field behavior of the antenna. Surface patch and wire grid models are compared and conclusions were presented. Keywords: Theses; Computer programs; Near fields; Numerical electromagnetics code; Wire grid; Surface patch; Admittance; Mono pole antenna. (jhd)