The direction of maximum radiation (also called the direction of the main beam) is one of the important features of the array.
The maximum radiation is obtained when
. If the direction of maximum radiation is denoted by we have
The array phase in terms of the direction of main beam is written as
Two things can be noted from the equation.
(1)
The direction of the maximum radiation is independent of the number of elements in the array.
(2) The direction of the main beam can be changed from 0 to by changing the progressive phase shift from .
An array is said to be End-fire array if the main beam is along the axis of the array. An array is said to be Broadside array if the main beam is perpendicular to the axis of the array.
There are two end-fire directions for an array but the broadside is a plane perpendicular to the array axis (see Fig below)
. If the direction of maximum radiation is denoted by 
we have 
by changing the progressive phase shift 
from 
. 
