Mutual coupling between two arbitrarily oriented and positioned antennas in near- and far-field regions

A flexible and efficient computer program is developed to compute complex amplitude coupling between two arbitrarily oriented and positioned antennas in near- and far-field regions. The program only requires as input complex vector farfield patterns of the two antennas and geometry of the coupling scenario. While theoretical development is almost entirely based on previous work in the literature, the current work improves upon prior results in two aspects: (1) movement of one of the two antennas is not restricted to a plane, (2) antenna orientations are allowed to vary as a function of antenna locations in space. Furthermore, it is shown that asymptotic evaluation of the coupling integral yields Friis´ transmission equation identically. Results from the current work show excellent agreement with those previously reported in the literature as well as coupling values obtained from a commercial 3-D moment method full-wave analysis software.