In wave theory, a phased array is an array of antennas

Antenna array (electromagnetic)

An antenna array is a group of isotropic radiators such that the currents running through them are of different amplitudes and phases. These are radiators of electromagnetic frequency and energy. Antenna arrays are the solution to the problem defined as the limitations of operating a single antenna...

 in which the relative phases

Phase (waves)

Phase in waves is the fraction of a wave cycle which has elapsed relative to an arbitrary point.-Formula:The phase of an oscillation or wave refers to a sinusoidal function such as the following:...

 of the respective signals feeding the antennas are varied in such a way that the effective radiation pattern

Radiation pattern

In the field of antenna design the term radiation pattern most commonly refers to the directional dependence of the strength of the radio waves from the antenna or other source ....

 of the array is reinforced in a desired direction and suppressed in undesired directions.

An antenna array

Antenna array

Antenna array may refer to:*Antenna array a group of isotropic radiators such that the currents running through them are of different amplitudes and phases*Interferometric array of radio telescopes used in radio astronomy...

 is a group of multiple active antennas coupled to a common source or load to produce a directive radiation pattern.