Smart antennas (also known as adaptive array antennas, digital antenna arrays, multiple antennas and, recently,

MIMO In radio, multiple-input and multiple-output, or MIMO (), is a method for multiplying the capacity of a radio link using multiple transmission and receiving antennas to exploit multipath propagation. MIMO has become an essential element of wi ...

) are

antenna array 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 individual antennas (called ''elements'') are usually connected to a single receiver o ...

s with smart

signal processing Signal processing is an electrical engineering subfield that focuses on analyzing, modifying and synthesizing '' signals'', such as sound, images, and scientific measurements. Signal processing techniques are used to optimize transmissions, ...

algorithm In mathematics and computer science, an algorithm () is a finite sequence of rigorous instructions, typically used to solve a class of specific problems or to perform a computation. Algorithms are used as specifications for performing ...

s used to identify spatial signal signatures such as the

direction of arrival In signal processing, direction of arrival (DOA) denotes the direction from which usually a propagating wave arrives at a point, where usually a set of sensors are located. These set of sensors forms what is called a sensor array. Often there is the ...

(DOA) of the signal, and use them to calculate

beamforming Beamforming or spatial filtering is a signal processing technique used in sensor arrays for directional signal transmission or reception. This is achieved by combining elements in an antenna array in such a way that signals at particular angles e ...

vectors which are used to track and locate the antenna beam on the mobile/target. Smart antennas should not be confused with reconfigurable antennas, which have similar capabilities but are single element antennas and not antenna arrays. Smart antenna techniques are used notably in acoustic signal processing, track and scan

radar Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, Marine radar, ships, spacecraft, guided missiles, motor v ...

radio astronomy Radio astronomy is a subfield of astronomy that studies celestial objects at radio frequencies. The first detection of radio waves from an astronomical object was in 1933, when Karl Jansky at Bell Telephone Laboratories reported radiation comin ...

and

radio telescope A radio telescope is a specialized antenna and radio receiver used to detect radio waves from astronomical radio sources in the sky. Radio telescopes are the main observing instrument used in radio astronomy, which studies the radio frequency ...

s, and mostly in cellular systems like

W-CDMA The Universal Mobile Telecommunications System (UMTS) is a third generation mobile cellular system for networks based on the GSM standard. Developed and maintained by the 3GPP (3rd Generation Partnership Project), UMTS is a component of the Int ...

UMTS The Universal Mobile Telecommunications System (UMTS) is a third generation mobile cellular system for networks based on the GSM standard. Developed and maintained by the 3GPP (3rd Generation Partnership Project), UMTS is a component of the In ...

, and LTE. Smart antennas have many functions: DOA estimation,

, interference nulling, and constant modulus preservation..

Direction of arrival (DOA) estimation

The smart antenna system estimates the direction of arrival of the signal, using techniques such as

MUSIC Music is generally defined as the art of arranging sound to create some combination of form, harmony, melody, rhythm or otherwise expressive content. Exact definitions of music vary considerably around the world, though it is an aspe ...

(MUltiple SIgnal Classification),

estimation of signal parameters via rotational invariance techniques In estimation theory, estimation of signal parameters via rotational invariant techniques (ESPRIT) is a technique to determine parameters of a mixture of sinusoids in a background noise. This technique is first proposed for frequency estimation, h ...

(ESPRIT) algorithms,

Matrix Pencil In linear algebra, if A_0, A_1,\dots,A_\ell are n\times n complex matrices for some nonnegative integer \ell, and A_\ell \ne 0 (the zero matrix), then the matrix pencil of degree \ell is the matrix-valued function defined on the complex numbers L(\ ...

method or one of their derivatives. They involve finding a spatial spectrum of the antenna/sensor array, and calculating the DOA from the peaks of this spectrum. These calculations are computationally intensive. Matrix Pencil is very efficient in case of real time systems, and under the correlated sources.

Beamforming

Beamforming Beamforming or spatial filtering is a signal processing technique used in sensor arrays for directional signal transmission or reception. This is achieved by combining elements in an antenna array in such a way that signals at particular angles e ...

is the method used to create the

radiation pattern In the field of antenna design the term radiation pattern (or antenna pattern or far-field pattern) refers to the ''directional'' (angular) dependence of the strength of the radio waves from the antenna or other source.Constantine A. Balanis: “A ...

of the antenna array by adding constructively the phases of the signals in the direction of the targets/mobiles desired, and nulling the pattern of the targets/mobiles that are undesired/interfering targets. This can be done with a simple Finite Impulse Response (FIR) tapped delay line filter. The weights of the FIR filter may also be changed adaptively, and used to provide optimal beamforming, in the sense that it reduces the

Minimum Mean Square Error In statistics and signal processing, a minimum mean square error (MMSE) estimator is an estimation method which minimizes the mean square error (MSE), which is a common measure of estimator quality, of the fitted values of a dependent variable. In ...

between the desired and actual beampattern formed. Typical algorithms are the steepest descent, and Least Mean Squares algorithms. In digital antenna arrays with multi channels use the digital beamforming, usually by DFT or FFT.

Types of smart antennas

Two of the main types of smart antennas include switched beam smart antennas and adaptive array smart antennas. Switched beam systems have several available fixed beam patterns. A decision is made as to which beam to access, at any given point in time, based upon the requirements of the system. Adaptive arrays allow the antenna to steer the beam to any direction of interest while simultaneously nulling interfering signals. Beamdirection can be estimated using the so-called direction-of-arrival (DOA) estimation methods. In 2008, the United States NTIA began a major effort to assist consumers in the purchase of digital television converter boxes. Through this effort, many people have been exposed to the concept of smart antennas for the first time. In the context of consumer electronics, a "smart antenna" is one that conforms to the EIA/

CEA-909 CEA-909 is the ANSI standard for 8VSB/ATSC smart antennas. The basic concept is that the smart antenna either physically rotates toward the signal, or is stationary, but has elements pointed in different directions and uses only those elements tha ...

Standard Interface. In 2017, the Israeli Aerospace Industries unveiled an adaptive array antenna called

ADA Ada may refer to: Places Africa * Ada Foah, a town in Ghana * Ada (Ghana parliament constituency) * Ada, Osun, a town in Nigeria Asia * Ada, Urmia, a village in West Azerbaijan Province, Iran * Ada, Karaman, a village in Karaman Province, T ...

, and stated that it is already operational and shall be fitted onto "major platforms" used by the

Israel Defense Forces The Israel Defense Forces (IDF; he, צְבָא הַהֲגָנָה לְיִשְׂרָאֵל , ), alternatively referred to by the Hebrew-language acronym (), is the national military of the Israel, State of Israel. It consists of three servic ...

Limited choice of EIA/CEA-909A smart antennas in the marketplace

Prior to the final transition to ATSC

digital television Digital television (DTV) is the transmission of television signals using digital encoding, in contrast to the earlier analog television technology which used analog signals. At the time of its development it was considered an innovative adva ...

in the United States on 11 June 2009, two smart antenna models were brought to market: * RCA ANT2000 – no longer available from retailers * DTA-5000 – manufactured by Funai Electric, marketed under the "DX Antenna" brand name, sometimes associated with the Sylvania brand name; no longer available from retailers And two models are causing consumer confusion: * Although the Apex SM550 is capable of connecting to a CEA-909 port for the purpose of drawing electrical power, it is not a true smart antenna. * The

Channel Master Channel Master is a manufacturer of TV Antennas and Accessories. History The original company, now defunct, was founded in Ellenville, New York, in 1949 by 23 year-old former Merchant Marine radio operator and DuMont TV antenna installer ...

3000A and CM3000HD SMARTenna series are otherwise-conventional amplified omnidirectional antennas, not steerable smart antennas. * ADA - An adaptive antenna produced by MLM factory of the Israel Aerospace Industries

Extension of smart antennas

Smart antenna systems are also a defining characteristic of

systems, such as the

IEEE The Institute of Electrical and Electronics Engineers (IEEE) is a 501(c)(3) professional association for electronic engineering and electrical engineering (and associated disciplines) with its corporate office in New York City and its operati ...

802.11n standard. Conventionally, a smart antenna is a unit of a wireless communication system and performs spatial signal processing with multiple antennas. Multiple antennas can be used at either the transmitter or receiver. Recently, the technology has been extended to use the multiple antennas at both the transmitter and receiver; such a system is called a multiple-input multiple-output (MIMO) system. As extended Smart Antenna technology, MIMO supports spatial information processing, in the sense that conventional research on Smart Antennas has focused on how to provide a digital beamforming advantage by the use of spatial signal processing in wireless channels. Spatial information processing includes spatial information coding such as Spatial multiplexing and Diversity Coding, as well as beamforming.

References

External links

Smart Antenna Research Group
at Stanford
Virginia Tech, Mobile and Portable & Radio research group
{{North American DTV Smart devices Radio frequency antenna types Antennas (radio)