10
Figure 5:
Radiation pattern of Isotropic (left) and Dipole (right) antennas
A higher gain typically indicates that the signal (transmitted or received) is concentrated
over a smaller beam width and can therefore cover a larger distance. However, the
effectiveness of a high gain antenna depends on the application. Typically, a high gain
antenna is most suitable for applications where the source or destination of the signal is
known in order to isolate a specific signal and avoid external interfering signals.
A lower gain typically indicates that the signal (transmitted or received) covers a wider
beam width and hence, a wider area. A low gain antenna is generally most suitable for
applications where either the source or the destination of the transmitted signal is not
known and hence, coverage in all directions from the antenna is required.
Antennas operate by concentrating the radio frequency energy they radiate or receive in
a beam of a particular width. The width of the beam is known as the antenna direction or
directivity.
The directional qualities of an antenna are known as being either unidirectional, bi-
directional or omnidirectional and each possesses its own coverage capabilities. A
unidirectional antenna is able to transmit or receive radio frequency energy in one
particular direction whereas a bi-directional antenna is able to do so in two particular
directions. An omnidirectional antenna is able to transmit or receive radio frequency
energy equally in all horizontal directions and is therefore able to achieve 360-degree
coverage.
Figure 6:
Unidirectional (left), Bi-directional (center) and Omnidirectional (right) antennas
3.4.2 Direction
