An array is simply a group of objects, and the array factor is a measure of how much a specific characteristic changes because of the grouping.
This phenomenon is observed when antennas are grouped together.
This is due to the constructive and destructive interference properties of radio waves.
A well designed antenna array, allows the broadcast power to be directed to where it is needed most.
In order to simplify the mathematics, a number of assumptions are typically made: The array factor
is the complex-valued far-field radiation pattern obtained for an array of
isotropic radiators located at coordinates
The array factor is defined in the transmitting mode,[2] with the time convention
A corresponding expression can be derived for the receiving mode, where a negative sign appears in the exponential factors, as derived in reference.