Page 197 - Antennas for Base Stations in Wireless Communications

170 Chapter Four

Figure 4.28 Roof-top mounted sector site con-
sisting of antenna unit with integrated ampli-
fiers, micro base station, and battery backup
unit (Courtesy of Ericsson)

power amplifiers are distributed along the antenna structure to gen-
erate power where it is most efficient, namely close to the radiating
elements. The power amplifiers are individually connected to subar-
rays of dual-polarized radiating elements. At the back of the transmit
array, cooling flanges are arranged from the bottom to the top of the
antenna unit to keep the temperature of the amplifiers low, even at
high ambient temperatures. The receive part of the antenna uses
polarization diversity and low-noise amplifiers connected directly to
each of the sum ports of the receive antenna elements. The antenna
unit is connected to a micro base station and a battery backup unit.
All units are compact and easy to install. Because an equipment room
is not needed, site acquisition becomes easy. The flexibility of the
concept makes it possible to build a rooftop three-sector site where
the three base stations are placed together in one spot or distributed
over the building. Three-sector sites can also be built in rural areas
without the need for heavy construction work, using existing struc-
tures and towers.