Antennas and multiplexer structures are provided for establishing
individual communication links with satellites that are located at
geostationary positions in close angular proximity to one another. The
antenna includes individual wave-guides where at least one of the
wave-guides has a decreased dimension such that the wave-guides may be
spaced in close proximity to each other to communicate with the
satellites. For example, in one embodiment, the antenna includes at least
one wave-guide that is a hollow metallic structure filled with a
dielectric material. The dimensions of this wave-guide can be altered by
changing the dielectric material used to fill the wave-guide. By using a
dielectric material having an appropriate dielectric constant, the
dimension of the wave-guide can be configured to allow the wave-guide to
be spaced in close proximity to the other wave-guide.