=== Directivity ===

As the name suggests, directivity is the measure of how directed the antenna radiation pattern is. That is how much an antenna transmits in a particular direction as opposed to transmitting uniformly in all directions. The radiation pattern can be depicted as a function of azimuth angle and elevation angle. The ratio of max power in radiation pattern function to the average power of radiation gives us the directivity of any antenna. Mathematically, if F(Θ,Φ) denotes the radiation function, directivity can be described by:

[[File:Directivity.JPG|center|frame]]

Based upon directivity, antennas can be divided in three groups:

* '''Isotropic:''' An isotropic antenna is an ideal antenna which radiates uniform power in all directions. Hence it's directivity would be 1(0 dB).

* '''Omnidirectional:''' Omnidirectional antenna radiates uniform power in a single plane and its power diminishes as we go away from the plane. Hence it's radiation pattern resembles a “doughnut”.