Array processing: Difference between revisions

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array processing concept was closely linked to radar and sonar systems which represent the classical applications of array processing. The antenna array is used in these systems to determine ___location(s) of source(s), cancel interference, suppress ground clutter. '''[[Radar|Radar systems]]''' used basically to detect objects by using radio waves. The range, altitude, speed and direction of objects can be specified. Radar systems started as military equipments then entered the civilian world. In radar applications, different modes can be used, one of these modes is the active mode. In this mode the antenna array based system radiates pulses and listens for the returns. By using the returns, the estimation of parameters such as velocity, range and DOAs (direction of arrival) of target of interest become possible. Using the passive far-field listening arrays, only the DOAs can be estimated. '''[[Sonar|Sonar systems]]''' (Sound Navigation and Ranging) use the sound waves that propagate under the water to detect objects on or under the water surface. Two types of sonar systems can be defined the active one and the passive one. In active sonar, the system emits pulses of sound and listens to the returns that will be used to estimate parameters. In the passive sonar, the system is essentially listening for the sounds made by the target objects. It is very important to note the difference between the radar system that uses radio waves and the sonar system that uses sound waves, the reason why the sonar uses the sound wave is because sound waves travel farther in the water than do radar and light waves. In passive sonar, the receiving array has the capability of detecting distant objects and their locations. Deformable array are usually used in sonar systems where the antenna is typically drawn under the water. In active sonar, the sonar system emits sound waves (acoustic energy) then listening and monitoring any existing echo (the reflected waves). The reflected sound waves can be used to estimate parameters, such as velocity, position and direction etc. Difficulties and limitations in sonar systems comparing to radar systems emerged from the fact that the propagation speed of sound waves under the water is slower than the radio waves. Another source of limitation is the high propagation losses and scattering. Despite all these limitations and difficulties, sonar system remains a reliable technique for range, distance, position and other parameters estimation for underwater applications.<ref name="ref2"/><ref name="ref6">{{citation |first1=Hema | last1= Singh |first2=RakeshMohan |last2=Jha| title=Trends in Adaptive Array Processing |year=2012}}</ref>

[[File:Radar System.png|thumb|Radar System]]

NORSAR is an independent geo-scientific research facility that was founded in Norway in 1968. NORSAR has been working with array processing ever since to measure seismic activity around the globe.<ref name=NORSAR>{{cite web|title=About Us|url=http://www.norsar.no/norsar/about-us/|publisher=NORSAR|accessdate=6 June 2013|archive-url=https://web.archive.org/web/20130620112533/http://www.norsar.no/norsar/about-us/|archive-date=20 June 2013|dead-url-status=yesdead}}</ref> They are currently working on an International Monitoring System which will comprise 50 primary and 120 auxiliary seismic stations around the world. NORSAR has ongoing work to improve array processing to improve monitoring of seismic activity not only in Norway but around the globe.<ref>{{cite web |url=http://www.norsar.no/pc-31-83-Improving-IMS-array-processing.aspx |title=Improving IMS array processing |publisher=Norsar.no |date= |accessdate=2012-08-06 |archive-url=https://web.archive.org/web/20120821220803/http://www.norsar.no/pc-31-83-Improving-IMS-array-processing.aspx |archive-date=2012-08-21 |dead-url-status=yesdead }}</ref>

* Communications (wireless)

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* {{cite book |title=Array Signal Processing |last1=Johnson |first1=D. H. |last2=Dudgeon |first2=D. E. |year= 1993|publisher=Prentice Hall}}

* {{cite book|first1=H. L.|last1=Van Trees|title=Optimum Array Processing|publisher=Wiley|___location=New York|year=2002}}

* {{cite journal|first1=H.|last1=Krim|first2=M.|last2=Viberg|url=http://www.vissta.ncsu.edu/publications/ahk/spm1996.pdf|title=Two Decades of Array Signal Processing Research|journal=IEEE Signal Processing Magazine|pages=67–94|date=July 1996|accessdate=8 December 2010|archive-url=https://web.archive.org/web/20130909011148/http://www.vissta.ncsu.edu/publications/ahk/spm1996.pdf|archive-date=9 September 2013|dead-url-status=yesdead}}

* S. Haykin and K.J.R. Liu (Editors), "Handbook on Array Processing and Sensor Networks", Adaptive and Learning Systems for Signal Processing, Communications, and Control Series, 2010.

* E. Tuncer and B. Friedlander (Editors), "Classical and Modern Direction-of-Arrival Estimation", Academic Press, 2010.