Can You Define Antenna Gain?

July 24, 2014 at 10:00 AM


"What is gain?" 


Many of our customers ask us this question. 


In fact, it has become so common that we created a Wireless Glossary to explain “gain” along with other common wireless terms.


But, the term “gain” is tricky to define, so we're going to dig into it a bit more here.


One of the major parameters used in analyzing the performance of radio frequency (RF) communication 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)






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.


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


To increase the directivity of a bulb's light (or 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 the light bulb now appears to be much brighter in the light beam. The amount that the bulb appears brighter compared to the bulb without a reflector is the directivity of the reflector (antenna).


When 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 also be noted that many factors need to be considered when selecting the "best" antenna for the desired application, and it’s best to discuss any antenna selection with someone knowledgeable in RF radiation and antenna performance. L-com has experts to help you make the best selection for performance and price to fit your application.



Helpful definitions to summarize our topic:


Antenna Gain: A relative measurement of an antenna's ability to direct or concentrate radio frequency energy in a particular direction or pattern. This 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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