Predicting power transfer between large aperture antennas at close separations

To obtain a reduction in the separation requirement for the prediction of antenna power transfer, a general power transfer formula is developed with no direct restriction on separation. This general formula is applied to the special case of two rectangular aperture antennas. The result is expressed in the form of the Friis transmission formula multiplied by two correction factors which are derived for six combinations of aperture illuminations. Results are presented of an experimental program to check the validity of the prediction method described. These results are in very close agreement with the theoretical prediction.