The original RF Cafe Forums were shut down in late 2012 due to maintenance issues
- primarily having to spend time purging garbage posts from the board. At some point
I might start the RF Cafe Forums again if the phpBB software gets better at filtering
Below are the old forum threads, including responses to the original posts.
Hey there is a great article linked from the RF
Cafe home page on near-field vs. far-field. Definitely
worth reading. Good find Kurt.
Post subject: Re: Near-Far Field
Posted: Mon Oct 10, 2005 5:20 pm
Joined: Tue Aug 09, 2005
1:07 pm Posts: 28
Hey there is a great article linked from the
RF Cafe home page on near-field vs. far-field.
Definitely worth reading. Good find Kurt.
a link would be nice. Couldn't find the
article on the main page
Posted: Mon Oct 10, 2005 9:28 pm
Joined: Sun Aug 03, 2003
2:02 pm Posts: 308 Location: Erie, PA
The article is
titled, "The World of the Near Fied," and the link
to it is in the Recent Additions list in the right
column. The link is replicated here so you don't
have to go back to the homepage to get to it. I
will be adding a calculator page for obtaining the
three near field boundary distances given in the
Excellent article. For me, its a setback. I always
knew to get the probes more than a couple of wavelengths
away from the antenna, or more than about 4 antenna
dimensions away, whichever was the larger.
That is such a gross rule of thumb, especially
in the face of all the graphs this author uses.
The concept explanations originally taught to
me about how the energy storage near fields were
different in nature to the one that radiates at
the speed of light, left a bit to be desired. Here
is where I just had to put my faith in the formulae
out of the books, without *really* understanding.
Post subject: near field for parabolic antennas
Posted: Mon Oct 24, 2005 10:23 am
Hay all, If we are on the subject of near field,
how would you define the near field of a parabolic
dish? I mean if you take a 10ft dish operating
at 5GHz you'll get a very large near field area
by using the standard rules. So do you use the
dish size to evaluate the far field or you use
size and thus get that the dish is actualy at the
far field of the feed?