Evaluation of the mutual coupling between shipborne antennas

Mutual coupling between shipborne antennas must be evaluated in order to establish power and frequency restraints on the corresponding equipment. Since shipborne communication antennas (including submarine surface communication antennas) are typically monopoles on bounded ground planes (e.g. different surfaces of the ship deck superstructure), the calculation of current distribution on each radiating element must take into account the proximity of the ground bounding edges. This issue proposes a hybrid selective method based on the selection between several concepts: geometrical theory of diffraction (GTD), uniform theory of diffraction (UTD), and geometrical optics (GO). The aim of this selection is to provide an improved computing approach, faster than traditional full-wave methods. Unlike other similar approaches, the UTD (which is the most time-costing of the above concepts) is only used for source-point/field-point couples that really need it. Modified Green functions are calculated and used with Hallen´s integral equations. The results of the proposed method are validated by measurements on a couple of monopoles on small size ground planes, placed in an anechoic chamber.