RLX2-IHx Series ♦ 802.11a, b, g, n
Appendix G - Antenna Configuration
Industrial Hotspots
User Manual
ProSoft Technology, Inc.
Page 220 of 248
13.1.2 Antenna Pattern
Wireless devices transfer Information using electromagnetic energy radiated by one
antenna and received by another antenna. The power radiated by most antennas is not
uniform in all directions and has varying intensities. The power radiated by the antenna
in various directions is called the
pattern
of the antenna. Mount each antenna so that the
direction of strongest radiation points toward the other antenna or antennas with which it
will exchange signals.
Complete antenna patterns are three-dimensional. Often only a two-dimensional slice of
the pattern is shown when all the antennas of interest are located in roughly the same
horizontal plane instead of above or below one another. A slice taken in a horizontal
plane through the center (or looking down onto the pattern) is called the
azimuth pattern
.
A slice taken in a vertical plan from the side is called the
elevation pattern
.
An antenna pattern with equal or nearly equal intensity in all directions is called
omnidirectional
. In two dimensions, an omnidirectional pattern appears as a circle (in
three dimensions, an omnidirectional antenna pattern is a sphere, but no antenna has a
true omnidirectional pattern in three dimensions). An antenna is considered
omnidirectional if one of its two dimensional patterns, either azimuth or elevation pattern,
is omnidirectional.
Beamwidth
is an angular measurement of how strongly the power is concentrated in a
particular direction. Beamwidth is a three dimensional quantity but can be broken into
two-dimensional slices just like the antenna pattern. The beamwidth of an
omnidirectional pattern is 360 degrees because the power is equal in all directions.
13.1.3 Antenna Gain
Antenna gain
is a measure of how strongly an antenna radiates in its direction of
maximum intensity compared to the strength of the radiation if the same power were
applied to an omnidirectional antenna (one that radiated all of its power equally in all
directions). In the antenna pattern, the gain is the distance to the furthest point on the
pattern from the origin. For an omnidirectional pattern, the gain is 1, or equivalently 0 dB.
The higher the antenna gain, the narrower the beamwidth, and
vice versa
.
The amount of power received by the receiving antenna is proportional to the transmitter
power multiplied by the transmit antenna gain, multiplied by the receiving antenna gain.
Therefore, you can make trade-offs between the antennas' gain and transmitting power.
For example, doubling the gain of one of the antennas has the same effect as doubling
the transmitting power. Doubling the gain for both antennas has the same effect as
quadrupling the transmitting power.