Antenna array

directional arrayplanar arrayarrayarray antennaarray antennasantenna arraysarraysdirectional antennadirectional antenna arraydirectional
An antenna array (or array antenna) is a set of multiple connected antennas which work together as a single antenna, to transmit or receive radio waves.wikipedia
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Phased array

phased array radarphased-arrayphased-array radar
Some antenna arrays (such as military phased array radars) are composed of thousands of individual antennas.
In antenna theory, a phased array usually means an electronically scanned array, a computer-controlled array of antennas which creates a beam of radio waves that can be electronically steered to point in different directions without moving the antennas.

Driven element

active devicesdrivenelement
The term antenna array most commonly means a driven array consisting of multiple identical driven elements all connected to the receiver or transmitter.
In a multielement antenna array (such as a Yagi-Uda antenna), the driven element or active element is the element in the antenna (typically a metal rod) which is electrically connected to the receiver or transmitter.

Antenna (radio)

antennaantennasradio antenna
An antenna array (or array antenna) is a set of multiple connected antennas which work together as a single antenna, to transmit or receive radio waves.
The antenna array and very similar reflective array antenna consist of multiple elements, often half-wave dipoles, spaced out on a plane and wired together with transmission lines with specific phase lengths to produce a single in-phase signal at the output.

Dipole antenna

dipolehalf-wave dipoledipoles
Small antennas around one wavelength in size, such as quarter-wave monopoles and half-wave dipoles, don't have much directivity (gain); they are omnidirectional antennas which radiate radio waves over a wide angle.
Although they may be used as standalone low-gain antennas, they are also employed as driven elements in more complex antenna designs such as the Yagi antenna and driven arrays.

Diversity scheme

diversitydiversity receptiondiversity gain
Arrays can be used to achieve higher gain, to give path diversity (also called MIMO) which increases communication reliability, to cancel interference from specific directions, to steer the radio beam electronically to point in different directions, and for radio direction finding (RDF).
Space diversity: The signal is transmitted over several different propagation paths. In the case of wired transmission, this can be achieved by transmitting via multiple wires. In the case of wireless transmission, it can be achieved by antenna diversity using multiple transmitter antennas (transmit diversity) and/or multiple receiving antennas (reception diversity). In the latter case, a diversity combining technique is applied before further signal processing takes place. If the antennas are far apart, for example at different cellular base station sites or WLAN access points, this is called macrodiversity or site diversity. If the antennas are at a distance in the order of one wavelength, this is called microdiversity. A special case is phased antenna arrays, which also can be used for beamforming, MIMO channels and space–time coding (STC).

Directivity

directive gaindirectionalsound diffusion
Small antennas around one wavelength in size, such as quarter-wave monopoles and half-wave dipoles, don't have much directivity (gain); they are omnidirectional antennas which radiate radio waves over a wide angle. An antenna array can achieve higher gain (directivity), that is a narrower beam of radio waves, than could be achieved by a single element.
In an antenna array (a set of multiple identical antennas which work together as a single antenna), the directivity of the entire array is the multiplicative sum of the individual antenna's directivity function with a mathematical expression known as the array factor AF, which typically depends on the location, the excitation and the phase of each antenna element.

Collinear antenna array

Collinearcollinear arrayscollinear (or co-linear) antenna array
Collinear array - a broadside array consisting of multiple identical dipole antennas oriented vertically in a line. This is a high gain omnidirectional antenna, often used in the VHF band as base station antennas for land mobile services.
In telecommunications, a collinear antenna array is an array of dipole antennas mounted in such a manner that the corresponding elements of each antenna are parallel and collinear, that is they are located along a common line or axis.

Active electronically scanned array

AESAactive phased arrayAESA radar
Active Electronically Scanned Array (AESA) - A phased array in which each antenna element has its own transmitter and/or receiver module, controlled by a central computer. This second generation phased array technology can radiate multiple beams at multiple frequencies simultaneously, and is mostly used in sophisticated military radars.
An active electronically scanned array (AESA) is a type of phased array antenna, which is a computer-controlled array antenna in which the beam of radio waves can be electronically steered to point in different directions without moving the antenna.

Reflective array antenna

Reflective arrayreflectarraybedspread array
Reflective array - a planar array of antennas, often half-wave dipoles fed in phase, in front of a flat reflector such as a metal plate or wire screen. This radiates a single beam of radio waves perpendicular (broadside) to the array. Used as UHF television antennas and radar antennas.
They are a type of array antenna.

Smart antenna

smart antennasantennaantenna array
Smart antenna, reconfigurable antenna or adaptive array - a receiving array that estimates the direction of arrival of the radio waves and electronically optimizes the radiation pattern adaptively to receive it, synthesizing a main lobe in that direction. Like a phased array it consists of multiple identical elements with phase shifters in the feed lines, controlled by a computer.
Smart antennas (also known as adaptive array antennas, digital antenna arrays, multiple antennas and, recently, MIMO) are antenna arrays with smart signal processing algorithms used to identify spatial signal signatures such as the direction of arrival (DOA) of the signal, and use them to calculate beamforming vectors which are used to track and locate the antenna beam on the mobile/target.

Passive radiator

parasitic elementparasiticparasitic radiator
A parasitic array consists of a single driven element connected to the feedline, and other elements which are not, called parasitic elements.
Antenna array (electromagnetic)

Very high frequency

VHFVHF radioVHF band
Collinear array - a broadside array consisting of multiple identical dipole antennas oriented vertically in a line. This is a high gain omnidirectional antenna, often used in the VHF band as base station antennas for land mobile services.
For even higher gain, multiple Yagis or helicals can be mounted together to make array antennas.

Loop antenna

loopstick antennasloop aerialloopstick antenna
Quad antenna - This consists of multiple loop antennas in a line, with one driven loop and the others parasitic. Functions similarly to the Yagi antenna.
Additional gain (and a uni-directional radiation pattern) is usually obtained with an array of such elements either as a driven endfire array or in a Yagi configuration (with all but one loop being parasitic elements).

Total active reflection coefficient

* Total active reflection coefficient
The TARC is mainly used for multiple-input multiple-output (MIMO) antenna systems and array antennas, where the outgoing power is unwanted reflected power.

Patch antenna

Patchpatch elements
Microstrip antenna - an array of patch antennas fabricated on a printed circuit board with copper foil on the reverse side functioning as a reflector. The elements are fed through striplines made of copper foil. Used as UHF and satellite television antennas.
Multiple patch antennas on the same substrate (see image) called microstrip antennas, can be used to make high gain array antennas, and phased arrays in which the beam can be electronically steered.

Log-periodic antenna

log periodic antennalog-periodiclog periodic
Log periodic dipole array (LPDA) - an endfire array consisting of many dipole driven elements in a line, with gradually increasing length. It acts as a high gain broadband antenna. Used as television reception antennas and for shortwave communication.
An antenna array consisting of two such antennas, one above the other and driven in phase has a gain of up to 17 dBi.

Radio wave

radio wavesradioradio signal
An antenna array (or array antenna) is a set of multiple connected antennas which work together as a single antenna, to transmit or receive radio waves.

Radio receiver

receiverreceiversRadios
The individual antennas (called elements) are usually connected to a single receiver or transmitter by feedlines that feed the power to the elements in a specific phase relationship.

Transmitter

radio transmittertransmittersradio transmitters
The individual antennas (called elements) are usually connected to a single receiver or transmitter by feedlines that feed the power to the elements in a specific phase relationship.

Feed line

feedlinefeeder linefeeding line
The individual antennas (called elements) are usually connected to a single receiver or transmitter by feedlines that feed the power to the elements in a specific phase relationship.

Superposition principle

superpositionlinear superpositionsuperpose
The radio waves radiated by each individual antenna combine and superpose, adding together (interfering constructively) to enhance the power radiated in desired directions, and cancelling (interfering destructively) to reduce the power radiated in other directions.

Antenna gain

gaindirective gaingain of an antenna
Small antennas around one wavelength in size, such as quarter-wave monopoles and half-wave dipoles, don't have much directivity (gain); they are omnidirectional antennas which radiate radio waves over a wide angle. An antenna array can achieve higher gain (directivity), that is a narrower beam of radio waves, than could be achieved by a single element.

MIMO

multiple-input multiple-outputmultiple-input and multiple-outputmultiple-input multiple-output communications
Arrays can be used to achieve higher gain, to give path diversity (also called MIMO) which increases communication reliability, to cancel interference from specific directions, to steer the radio beam electronically to point in different directions, and for radio direction finding (RDF).

Null (radio)

nullcancelspatial nulls
Arrays can be used to achieve higher gain, to give path diversity (also called MIMO) which increases communication reliability, to cancel interference from specific directions, to steer the radio beam electronically to point in different directions, and for radio direction finding (RDF).

Electromagnetic interference

interferenceradio frequency interferenceradio interference
Arrays can be used to achieve higher gain, to give path diversity (also called MIMO) which increases communication reliability, to cancel interference from specific directions, to steer the radio beam electronically to point in different directions, and for radio direction finding (RDF).