In telecommunication

Telecommunication

Telecommunication is the transmission of information over significant distances to communicate. In earlier times, telecommunications involved the use of visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, and optical heliographs, or audio messages via coded...

, a reflective array antenna is an antenna  in which multiple driven element

Driven element

In a multielement antenna array , the driven element or active element is the element in the antenna which is electrically connected to the receiver or transmitter. In a transmitting antenna it is driven or excited by the RF current from the transmitter, and is the source of the radio waves...

s are mounted in front of a surface designed to reflect the radio waves

Radio waves

Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light. Radio waves have frequencies from 300 GHz to as low as 3 kHz, and corresponding wavelengths from 1 millimeter to 100 kilometers. Like all other electromagnetic waves,...

 in a desired direction.

Reflective array antennas usually have many driven elements working in conjunction with a flat, electrically large reflecting surface

Reflector (antenna)

An antenna reflector is a device that reflects electromagnetic waves.It is often a part of an antenna assembly.The most common reflector types are...

 to produce a unidirectional

Directional antenna

A directional antenna or beam antenna is an antenna which radiates greater power in one or more directions allowing for increased performance on transmit and receive and reduced interference from unwanted sources....

 beam

Beam

Beam may refer to:*Beam , a construction element*Beam , the most extreme width of a nautical vessel, or a point alongside the ship at the mid-point of its length*A narrow, propagating stream of particles or energy:...

, increasing antenna gain

Antenna gain

In electromagnetics, an antenna's power gain or simply gain is a key performance figure which combines the antenna's directivity and electrical efficiency. As a transmitting antenna, the figure describes how well the antenna converts input power into radio waves headed in a specified direction...

 and reducing radiation

Radiation

In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...

 in unwanted directions. These are also called "billboard antennas". The reflector may be a metal sheet or more commonly a wire screen. They may contain parasitic elements as well as driven elements.

A metal screen reflects radio waves as well as a solid metal sheet as long as the holes in the screen are smaller than about one-tenth of a wavelength, so screens are often used to reduce weight and wind loads on the antenna.

Actually Reflect array antennas came into full existence from Year 1980 as a cross breed from the parabolic reflectors and array antenna theory. Utilizing Micro strips ,dipoles as preliminary radiating elements without power division transmission lines fed through Horn antenna reflect array antennas gained lot of popularity in terms of the Low weight and surface tolerances in compare to parabolic reflectors.

The feed element radiates the plane which is normal and the plane re radiates back the incident power onto the reflect array elements with electrical phases required to form the planar wave front. The re-radiating plane can be any polarizer with dielectric substrate filled or slotted wave guide.

The Polarizer helps to achieve either of one polarization in the sense if the feed is illuminated with the Horizontal polarization you can see Vertical polarization in the free space and vice versa , In order to achieve circular polarization the reflect array elements needed to have special properties such as two transmission line stubs with proper phase delay [2].