Antenna Gain for Dummies

July 14, 2016 at 8:00 AM

 

Many customers ask us to explain antenna gain, but it can be a little tricky to wrap your mind around. So, here we’ll break it down for you in our version of Antenna Gain for Dummies.

 

Antenna gain is the relative measure of an antenna’s ability to direct or concentrate radio frequency (RF) energy in a specific direction or pattern. Typically measured in decibels relative to an isotropic radiator (dBi) or decibels relative to a dipole radiator (dBd).

 

An Isotropic Radiator radiates energy equally in every direction, similar to a light bulb. The isotropic radiator antenna radiates uniformly and exhibits the same magnitude or properties when measured in all directions.

 

Why Antenna Gain Is Important:

 

One of the major factors used to analyze 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. 1.Transmitter power
  2. 2.The ability of the antenna(s) to direct that power toward an RF receiver(s)

 

Typically, antennas with higher gain will perform more efficiently and operate with a farther range distance.

  

How It’s Measured:

 

To determine the directivity of an antenna, a reference antenna is needed in order to compare performance. An isotropic radiator is the preferred antenna for comparison because it transmits equal amounts of power in all directions - like a light bulb.

 

To increase the directivity of the isotropic radiator, an antenna is added behind it to act like a reflector and direct the antenna’s energy - just like a reflector behind the bulb of a flashlight.

 

With the reflector, the flashlight will now appear much brighter, as will the energy of the antenna being pointed in one direction. Now the directivity can be calculated by measuring the difference between the antenna’s energy before and after the addition of the reflector. 

 

The directivity is then converted into decibels to determine the antenna gain relative to an isotropic source (dBi). For every 6 dBi in gain, you double the range of the antenna.

 

Now that you have a better understanding of antenna gain, there are still many factors to consider when selecting the right antenna for your application. In certain instances, too much gain can be a bad thing. 

 

For more information about antenna gain and other common wireless terms, check out our wireless glossary

 

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