Base Station Antennas

There are a multitude of antennas that can be used at a base station. However
the specifics of what comprise a base station antenna, or rather an
antenna system, is determined by the design objectives for the site coupled
with real world installation issues. For 3G radio systems as well as the 2.5G
radio systems, most, if not all, of the antenna design decisions are determined
by the type of base station they will be employed at. For instance the
antenna system for a macro cell will most likely be different than that used
for a micro and definitely different for a pico cell.
Base station antennas are either omni directional, referred to as omni, or
directional antennas. The antenna selected for the application should be
one that meets the following major points as a minimum:
■ Elevation and azimuth patterns meet requirements.
■ The antenna exhibits the proper gain desired.
■ The antenna is available from common stock and company inventory.
■ The antenna can be mounted properly at location, that is, it can be
physically mounted at the desired location.
■ Antennas will not adversely affect the tower, wind and ice loading for
the installation,
■ Visual impact, negative, has been minimized in the design and
selection phase.
■ Antenna meets the desired performance specifications required.
However this section will restrict itself to collinear, log periodic, folded
dipole, yagi, and microstrip antennas with respect to passive, that is, no
active electronics in the antenna system itself. Of the antennas classifications
mentioned, two are more common for use in 1G and 2G communication systems
for base stations and will be used for 2.5G and 3G also. The two types of
antennas used for base stations are collinear and log periodic antennas.