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Near vs. Far Field - RF Cafe Forums

The original RF Cafe Forums were shut down in late 2012 due to maintenance issues. Original posts:

Amateur Radio | Antennas | Circuits & Components | Systems | Test & Measurement


Jose Arrina
 Post subject: Near vs. Far Field
Posted: Thu Mar 30, 2006 9:23 am 
 
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Joined: Thu Mar 30, 2006 9:01 am
Posts: 4
Hi guys,

I have searched around the Internet for a definite definition of where the transition between near filed and far field lie. I see a lot of rules of thumb, and they vary from something like lambda/4 to 10*lambda. There has to be a truly technical definition that the measurement standard houses use. If would appreciate it if you could point me to one or more documents that declare ye verily this be the standard ;-).

Thanks, and have a good day.

_________________
... Jose' Arrina


 
   
 
Kirt Blattenberger
 Post subject
Posted: Thu Mar 30, 2006 1:13 pm 
 
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Joined: Sun Aug 03, 2003 2:02 pm
Posts: 308
Location: Erie, PA
Greetings Jose':

A while back, Evaluation Engineering published a good article on the subject (1). I used their equations to create a calculator (2) that you can plug the DUT antenna dimension into and get a table & graph. The definition given agrees with what a lot of other field measurement papers use for the near field and far field regions. Here is another paper to consider (3); Figure 3 is a good picture of what's happening.


(1) http://www.evaluationengineering.com/archive/articles/1005/1005the_world.asp

(2) http://www.rfcafe.com/references/electrical/near-far-field.htm

(3) http://www.conformity.com/0102reflections.html

.

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