On the Radiation Patterns of Interfacial Antennas
The radiation pattern of an interfacial radiating source is obtained for the case where the source is an infinitely long line source lying along the plane interface of two dielectric half-spaces; for the case where the source is an infinitesimal electric dipole vertically located on the interface; and for the case where the dipole is lying horizontally along the interface. For all the three cases, it is found that the radiation pattern at the interface has a null (interface extinction). For the
... xtinction). For the infinitely long line source, it is obtained that the pattern in the upper half-space, whose index of refraction is taken to be less than that of the lower half-space, has a single lobe with a maximum normal to the interface, and that the pattern in the lower half-space (subsurface region) has two maxima straddling symmetrically a minimum. Interpretation of these results in terms of ray optics, Oseen's extinction theorem, and the Cerenkov effect are given. For the vertical dipole, it is found that the radiation pattern along the dipole axis has a null. For the horizontal dipole, it is obtained that the pattern in the upper half-space has a single lobe whose maximum is normal to the interface; that in the lower half-space, in the plane normal to the interface and containing the dipole, the pattern has three lobes; whereas in the plane normal to the interface and normally bisecting the dipole, the pattern has two maxima located symmetrically about a minimum. Interpretation of these results in terms of the Cerenkov effect is also given.