The effect of dipole coupled impedances on open field range calibration

The half-wave dipole is the fundamental antenna used in the calibration of open-field test sites. Coupling among the antennas and their images causes a change in antenna center impedance, resulting in a correction of several decibels in the site attenuation model. A derivation of the method of calculating the effect of the coupled impedances is given along with a discussion of the correlations between the mathematical model and measurements on 3-m ranges. Resistive and reactive values are calculated separately. The Smith-German-Pate (1982) equations, expanded into separate resistive and reactive expressions, are then used to find the mutual impedances at the center of the transmit and receive antennas resulting from couplings among all the combinations of antennas and their images. The mutual resistances and reactances thus derived are then used to compute the delta antenna factor which is significant in bringing the mathematical model and the measurements on ranges into agreement