Radiation of a planar spiral antenna above a double-dielectric loaded ground plane

The radiation properties of a spiral antenna above a double-dielectric loaded ground plane are investigated analytically. The electromagnetic field components in the far field region are derived by using the Green's function formulation, while an appropriate model for the surface current distribution on the spiral antenna is used. This type of antenna has been found to be convenient for mobile telecommunication applications, since it is a wideband, circular-polarized, and omnidirectional one, with no radiation at the vertical and the horizontal axes, no side lobes, and a main lobe at an elevation angle that corresponds to a large region of latitudes. For a central operating frequency at 1.6 GHz, the antenna has been found to be significantly compact and therefore easily mounted on a car ceiling, without causing noticeable modifications to its appearance.<
>