Reflector antennas with directional effect in the near-field Characteristics and applications

The present investigation is concerned with the characteristics and applications of reflector antennas with a radiation field which is focused on a point in the antenna near field. Scalar diffraction theory is employed to study apertures with a spherical phase front and a convergence of the radiation in the focus. Particular attention is given to the radiation field of the rectangular and circular focusing aperture. The radiation field of elliptical reflectors is studied with the aid of a vectorial approximate calculation. An application area of focusing antennas related to position finding is considered, taking into account the antenna of a radar for monitoring an aircraft landing field. In this radar system, the considered objects are partly or entirely in the antenna near field. Applications related to antenna measurement techniques are also discussed, taking into account focusing in the case of a parabolic reflector and the computation of radiation patterns.