Correction factor for nonplanar incident field in monopole calibrations

In calibrating monopole antennas, the length of the antenna can be comparable to the separation distance. In that case, there is a significant variation in both the magnitude and the phase of the incident field along the length of the antenna under test. An expression for a correction factor is presented to account for this effect. The correction factor is evaluated for some representative cases, and some guidelines are given for when this factor should be taken into account. The effect can exceed 1 dB in some practical cases