View source for Engineering:Smart antenna

{{Short description|Antenna arrays with smart signal processing algorithms}}
 '''Smart antennas''' (also known as adaptive array antennas, [[Digital antenna array|digital antenna array]]s, multiple antennas and, recently, MIMO) are [[Physics:Antenna array|antenna array]]s with smart [[Signal processing|signal processing]] [[Algorithm|algorithm]]s used to identify spatial signal signatures such as the [[Direction of arrival|direction of arrival]] (DOA) of the signal, and use them to calculate [[Beamforming|beamforming]] vectors which are used to track and locate the antenna beam on the mobile/target. Smart antennas should not be confused with [[Engineering:Reconfigurable antenna|reconfigurable antenna]]s, 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 [[Engineering:Radar|radar]], [[Astronomy:Radio astronomy|radio astronomy]] and [[Astronomy:Radio telescope|radio telescope]]s, and mostly in [[3G|cellular systems]] like W-CDMA, [[UMTS]], and [[Engineering:LTE (telecommunication)|LTE]] and 5G-NR.<ref>{{cite web | url=https://www.isemag.com/5g-6g-and-fixed-wireless-access-mobile-evolution/article/14268016/the-role-of-smart-antennas-in-optimizing-5g | title=StackPath }}</ref>

Smart antennas have many functions: DOA estimation, [[Beamforming|beamforming]], 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 (MUltiple SIgnal Classification),  estimation of signal parameters via rotational invariance techniques (ESPRIT) algorithms, [[Matrix pencil|Matrix Pencil]] method or one of their derivatives. They involve finding a spatial spectrum of the antenna/[[Engineering:Sensor array|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]] is the method used to create the [[Engineering:Radiation pattern|radiation pattern]] 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|Minimum Mean Square Error]] 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 [[Fast Fourier transform|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.<ref>{{cite book |title=Smart Antennas for Wireless Communications: With MATLAB |series=Professional Engineering |author-first=Frank |author-last=Gross |date=2005 |edition=1 |publisher=McGraw-Hill Professional |isbn=978-0071447898}} (288 pages)</ref> Beamdirection can be estimated using the so-called direction-of-arrival (DOA) estimation methods.<ref>{{cite web |url=https://users.ece.utexas.edu/~bevans/courses/ee381k/lectures/13_Array_Processing/lecture13/lecture13.pdf |title=Array Processing Tutorial |website=The University of Texas at Austin}}</ref>

In 2008, the United States NTIA began a major effort to assist consumers in the purchase of [[Social:Coupon-eligible converter box|digital television converter boxes]].<ref>{{cite web |url=http://www.dtv2009.gov/ |title=Microsoft Redirect |website=www.dtv2009.gov |access-date=22 May 2022 |archive-url=https://web.archive.org/web/20071214091116/http://www.dtv2009.gov/ |archive-date=14 December 2007 |url-status=dead}}</ref> 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 Standard Interface.

In 2017, the Israeli Aerospace Industries unveiled an adaptive array antenna called [[Engineering:ADA (Smart antenna)|ADA]], and stated that it is already operational and shall be fitted onto "major platforms" used by the Israel Defense Forces.

==Limited choice of EIA/CEA-909A smart antennas in the marketplace==
Prior to the final transition to ATSC [[Engineering:Digital television|digital television]] 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 [[Company:Funai|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.<ref>[https://www.avsforum.com/forum/25-hdtv-technical/1008952-official-avs-smart-antenna-topic-4.html#post16553780 The Official AVS 'Smart Antenna' Topic - Page 4]. AVS Forum.</ref>
* The Channel Master 3000A and CM3000HD '''SMARTenna''' series are otherwise-conventional amplified omnidirectional antennas, not steerable smart antennas.<ref>[https://web.archive.org/web/20100120075430/http://www.solidsignal.com/pview.asp?p=anc3000 Channel Master CM 3000 Suburban Outdoor Amplified Omnidirectional SMARTenna TV Antenna (CM3000A)] at the Wayback Machine.</ref>
* '''ADA''' - An adaptive antenna produced by MLM factory of the Israel Aerospace Industries<ref>[http://www.iai.co.il/2013/37166-48168-en/ADA%20GNSS%20Anti-Jamming%20System.aspx ADA GNSS Anti-Jamming System]</ref>

==See also==
* {{annotated link|Engineering:Antenna (radio)}}
* {{annotated link|Array processing}}
* {{annotated link|Engineering:History of smart antennas}}
* {{annotated link|Engineering:Phased array}}
* {{annotated link|Organization:WiMAX}}
* {{annotated link|Engineering:Diversity combining}}
* {{annotated link|Engineering:Active antenna}}
* {{annotated link|Engineering:Reconfigurable antenna}}
* {{annotated link|Digital antenna array}}

==References==
{{Reflist}}

==Further reading==
* {{cite book |title=Handbook on Advancements in Smart Antenna Technologies for Wireless Networks |series=Premier Reference Source |publisher=IGI Global |date=2008 |edition=1 |author-first1=Chen |author-last1=Sun |author-first2=Jun |author-last2=Cheng |author-first3=Takashi |author-last3=Ohira |isbn=978-1599049885}} (584 pages)

==External links==
* [http://www.stanford.edu/group/sarg/ Smart Antenna Research Group] {{Webarchive|url=https://web.archive.org/web/20131020074439/http://www.stanford.edu/group/sarg/ |date=2013-10-20  }} at Stanford
* [https://wireless.vt.edu/ Virginia Tech, Mobile and Portable & Radio research group]

{{North American DTV}}

[[Category:Smart devices]]
[[Category:Radio frequency antenna types]]
[[Category:Antennas (radio)]]

{{Sourceattribution|Smart antenna}}