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btb4198 Antenna Theory Regular
Joined: 19 May 2011 Posts: 20

Posted: Thu May 19, 2011 5:38 pm Post subject: near field and far field 


ok so the r in R<< D is the radius of what? radius of antenna ? or radius of something else ? 

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Schubert Antenna Wizard
Joined: 08 Apr 2009 Posts: 161

Posted: Thu May 19, 2011 6:40 pm Post subject: 


It is R >> D.
R is the distance from the antenna where you are measuring the fields transmitted from the antenna.
R>>D is one of the requirements to be in the "far field" of the antenna. This means that if the antenna is of size D, then to be in the far field you must be at least 10*D away from the antenna. Note that this is only one of the requirements to be in the far field, all 3 conditions must be satisfied:
http://www.antennatheory.com/basics/fieldRegions.php 

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btb4198 Antenna Theory Regular
Joined: 19 May 2011 Posts: 20

Posted: Fri May 20, 2011 2:50 pm Post subject: 


D is the length of the antenna right?
R >> D
178m >> 0.03125m is true
R >> λ
178m >> 0.125 is true
R > ( 2D^2)/λ
178m > 0.015625m is true
so my point is in the Far Field, right? 

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bigSteve Antenna Wizard
Joined: 14 Mar 2009 Posts: 265

Posted: Fri May 20, 2011 5:23 pm Post subject: 


Yes, all the requirements are met to be in the far field. 

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