Development of a hemispherical near field antenna measurement range for use on a realistic ground

The present state of the art for the gain measurement of antennas on ground vehicles is to build a hemispherical scanner and then use a perfectly reflecting ground surface (so that reflection theory can "complete the sphere") or an absorbing floor (to eliminate ground reflections so that the below-ground spherical data can be set to zero.) Then, the data is transformed to the far field through the use of the spherical mode expansion technique. In this realistic ground scenario, we show the use of direct plane wave synthesis along with known values (bore-hole measurements) of the ground reflection coefficients to compute the ground vehicle antenna far field patterns.