Validation of the Numerical Electro-Magnetics Code (NEC) for Antenna Wire Elements in Proximity to Earth
MITRE CORP BEDFORD MA
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This paper summarizes recent MITRE efforts to validate the NEC-3, NEC-GS, and NEC-3I versions of the Numerical Electromagnetics Code NEC developed by Lawrence Livermore National Laboratory for predicting the performance of antenna wire elements in close proximity to flat earth. In an early version NEC-1, the effect of the air-ground interface was included by applying a plane-wave Fresnel reflection coefficient approximation to the field of a point source. The NEC-2 version, while still retaining the Fresnel reflection coefficient model as an option, provides a more accurate ground model by numerically evaluating Sommerfeld integrals. The version NEC-3 extends the NEC-2 version to cases for bare wire segments below the air-earth interface. Version NEC-GS utilizes rotational symmetry to provide a more efficient version of NEC-3 for the case of a monopole element with a uniform radial wire groundscreen GS. Version NEC-3I extends NEC-3 to include the case of insulated I wires.
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