Measurement and modeling of near- and far-field antenna factor

This paper summarizes a recent investigation into the measurement and modeling of antenna factor as a function of separation distance. Measurements were made of coupling and antenna factor (AF) for a standard gain dipole as a function of distance from an identical source. Coupling and AF were also computed using two electromagnetic computer codes to compare the numerical results with each other and with the measurements. The coupling measurements were made in an anechoic chamber using two identical standard gain dipoles at 300 MHz, both with and without a ground plane. In the case with a ground plane, both horizontal and vertical polarizations were examined. Distances were varied to cover from the very near-field to the far-field of the antenna. Measured values of the AF at 300 MHz were frequency scaled to predict the AF at 30 MHz. In addition to the measurements, the Numerical Electromagnetics Code (NEC) Method of Moments and the General Electromagnetic Model for the Analysis of Complex Systems (GEMACS) were used to calculate coupling and AF values for direct comparison with the measured values