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Antenna Gain - Vol. 9 No. 33
(Tuesday, July 07, 2009)
 
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What Does Antenna Gain Mean?
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Antenna Gain - What Does It Mean?

Many customers ask us "What is gain?" It is such a common question that we added a Wireless Glossary to explain gain and other common wireless terms.

But gain itself is a tricky term to define, so we're going to explain it here a little more in depth.

One of the major parameters used in analyzing the performance of radio frequency (RF) communications links is the amount of transmitter power directed toward an RF receiver.

This power is derived from a combination of:

  1. Transmitter power
  2. The ability of the antenna(s) to direct that power toward an RF receiver(s)
Directivity

The directivity of the antenna is determined by the antenna design. Directivity is the ability of an antenna to focus energy in a particular direction when transmitting or to receive energy better from a particular direction when receiving. To determine the directivity of an antenna, we need a reference antenna with which to compare our antenna's performance.

Omni Directional Antenna with 360 Degree Coverage Yagi Antenna with Directional Focused Coverage
Omni Directional:
360° Coverage
Directional:
Focused Coverage

Over the years there have been several different reference antennas used; however, today an isotropic radiator is preferred as the standard antenna for comparison. As noted, the isotropic antenna transmits equal amounts of power in all directions (like a light bulb).

To increase the directivity of a bulb's light (the antenna's energy), similar to a flash light or automobile head lamp in this example, a reflector (antenna) is added behind the bulb. At a distance, in the light beam, the light bulb now appears to be much brighter. The amount that the bulb appears brighter compared to the bulb without a reflector is the directivity of the reflector (antenna).

When the directivity is converted to decibels we call it the antenna gain relative to an isotropic source (dBi). Typically the higher the gain, the more efficient the antenna's performance, and the farther the range of the antenna will operate. For every 6 dBi in gain, you double the range of the antenna.

It should be noted that many issues need to be considered when selecting the "best" antenna for the application, and you should discuss any antenna selection with someone knowledgeable in RF radiation and antenna performance. L-com has the experts to help you make the "best" selection for performance and price, to fit your application.

Here are some more helpful terms and definitions:

Antenna Gain: A relative measure of an antenna's ability to direct or concentrate radio frequency energy in a particular direction or pattern. The measurement is typically measured in dBi (Decibels relative to an isotropic radiator) or in dBd (Decibels relative to a dipole radiator).

Isotropic Radiator: is a theoretical single point in space that radiates energy equally in every direction similar to the Sun radiating its light. The isotropic radiator exhibits the same magnitude or properties when measured in all directions. It has no preferred direction of radiation. It radiates uniformly in all directions over a sphere centered on the source.

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