Simulation of far-field characteristics and measurement techniques for vehicle-mounted antennas

Numerical models of simple monopoles mounted on vehicles are presented which indicate that the far-field gain and radiation patterns for such systems can differ significantly from that of the ideal antenna. The theoretical results also suggest that very significant antenna separations (>30 m) may be required in order to carry out gain measurements using simple transmission measurements for vehicles located on a conducting ground plane. The measured coupling to a test antenna at 5 m range is comparable with simulations based on a TLM model of this arrangement. These results give some confidence in the validity of the estimated far-field characteristics, since the latter were derived from predicted fields in this region.