Radio base stations for point-to-multipoint communications usually employ
arrays of antennas at a certain height from the ground for omnidirectional
coverage, with element excitations being exercised in order to achieve a
suitable elevation pattern synthesis. More recently, attention has been focused
on point-to-multipoint (not necessarily mobile ones, but fixed as well) services
such as broadband wireless (high-density fixed) systems for which compact
shaped reflector antennas comprise an interesting alternative to usual base
station arrays due to their ability in providing customized coverage patterns,
with bandwidth requirements now being met via adequate feed designs.
Prospective reflector designs, while producing cosecant squared-like power
patterns in the vertical plane to account for free space attenuation, should also
concentrate radiated energy bellow the horizon line for reduced interference.
One such configuration, explored in [1], involved a nodal station comprising up
to four shaped offset reflector antennas for quadrant sectors coverage, with
substantial design effort aimed at properly modeling the reflector surfaces [2].
Alternatively, a compact configuration employing a single circularly
symmetrical shaped reflector surface fed by an axial horn, has been investigated
in [3]. A specific design of the latter configuration is further explored herein
with a view towards evidencing the benefit of a strictly numerical analysis fool
such as the Method of Moments (MOM) for both reflector and feed structures,
as compared to the more conventional optical (geometrical and physical) route.
|