Computation of antenna side-lobe coupling in the near field using approximate far-field data

Computer programs, in particular CUPLNF and CUPLZ, are presently in existence to calculate the coupling loss between two antennas provided that the amplitude and phase of the far field are available. However, for many antennas the complex far field is not known accurately. In such cases it is nevertheless possible to specify approximate far fields from a knowledge of the sidelobe level of each antenna along the axis of separation, and the electrical size of each antenna. To determine the effectiveness of using approximate sidelobe level data instead of the detailed far fields, two hypothetical, linearly polarized, uniformly illuminated circular antennas for which the exact far fields are given by a simple analytic expression were chosen as test antennas.