What kind of radiation
pattern is desired?
This is the first major delineator of antenna selection.
The only way to increase gain is to concentrate power in a narrower
beamwidth. The narrower the beamwidth, the greater the gain of
A good conceptual example of this concentration is the vertical
omnidirectional antenna. It is often used for line-of-sight communications
with mobile stations spread out in various directions usually
restricted to the horizon. We don't have to warm the clouds,
do we! If greater performance is required, the antenna gain can
be increased by using a collinear type of omni that decreases
the vertical beamwidth and hence concentrates more power on the
horizon where it will be most beneficial. Figure 1 shows the
typical radiation pattern of a gain omni antenna.
Figure 1. Typical radiation pattern of a high gain omni antenna
Likewise, panel antennas are used to optimize a sector (typically
90 to 120 degrees in azimuth) with a narrow elevation beamwidth.
Yagis, parabolic dishes and patch arrays are usually designed
for high gain and hence have narrow beamwidths in both the azimuth
and elevation plane. A typical high gain Yagi antenna pattern
is shown in Figure 2. The gain can be further increased (and
the beamwidth narrowed) by mounting multiple identical antennas
in an array and properly spacing the antennas to account for
Figure 2. Typical radiation pattern of high gain Yagi antenna
Astron Wireless Technologies,
Inc. and the author retain the rights to all intellectual property
This information should be used as a guideline
only to help you in the appropriate selection of an antenna.