Beam offset using a loaded-aperture cavity-backed slot antenna

Lending an aperture-coupled cavity-backed slot antenna with a metal post is shown to produce an asymmetrical field distribution in the slot aperture. This field distribution gives rise to a far-field pattern which is directed away from the boresight of the antenna. Theoretical and experimental resul ts are presented which show the amount of beam offset that can be obtained for various diameter posts inserted into a cavity coupled to free space by a radiating aperture of width 0.1 lambda-0.25 lambda and length 0.5 lambda. These results show that up to 13 degrees of beam offset can be achieved wi th this approach. The method suggested has potential as a cellular base-sta tion antenna element in situations where downtilt coverage is required. (C) 1999 John Wiley & Sons, Inc.