Definition of Directivity
In electromagnetics, directivity is a parameter of an antenna or optical system which measures the degree to which the radiation emitted is concentrated in a single direction. It is the ratio of the radiation intensity in a given direction from the antenna to the radiation intensity averaged over all directions. Therefore, the directivity of a hypothetical isotropic radiator, a source of electromagnetic waves which radiates the same power in all directions, is 1, or 0 dBi.
An antenna's directivity is greater than its gain by an efficiency factor, radiation efficiency. Directivity is an important measure because many antennas and optical systems are designed to radiate electromagnetic waves in a single direction or over a narrow-angle. By the principle of reciprocity, the directivity of an antenna when receiving is equal to its directivity when transmitting.
The directivity of an actual antenna can vary from 1.76 dBi for a short dipole to as much as 50 dBi for a large dish antenna.
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Frequently asked questions
What is Directivity?
In electromagnetics, directivity is a parameter of an antenna or optical system which measures the degree to which the radiation emitted is concentrated in a single direction.
Sources & credits
- Wikipedia: Directivity – CC BY-SA 4.0
- Image by Timothy Truckle – CC BY-SA 4.0