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how can we create a capacitive loading

 
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Rfdesign
Antenna Theory Regular


Joined: 31 Dec 2011
Posts: 16

PostPosted: Fri Jan 06, 2012 5:55 pm    Post subject: how can we create a capacitive loading Reply with quote

hi
in the following figure
http://www.antenna-theory.com/antennas/patches/pifa.php
I want to know :
what's the effect of this loading?
Do we put something in the mentioned position to create the capacitive loading ?if yes ,what?
Is it like a short pin?just a pin or not?
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Schubert
Antenna Wizard


Joined: 08 Apr 2009
Posts: 161

PostPosted: Fri Jan 06, 2012 11:26 pm    Post subject: Reply with quote

The capacitive loading can be done with a small capacitor. A short pin will not work.

You can also just raise a plate from the ground near the top of the patch which will also capacitively load. The capacitive loading allows you to shrink the size of the antenna, at the expense of antenna efficiency and bandwidth.

The capacitive side of the patch is to the left as shown in the figure, which must be balanced by the right (inductive) side for proper matching and radiation.
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Rfdesign
Antenna Theory Regular


Joined: 31 Dec 2011
Posts: 16

PostPosted: Sun Jan 08, 2012 12:16 pm    Post subject: Reply with quote

Dear Schubert
Thanks for your useful reply
you mean the capacitive loading is something like this:



That is from the ground plant to the patch position and on the other side of the short pin?Am I true?
but another question here is that ,I found that by changing the short pin position I can actually tune the antenna in a desired frequency.
Can I change the bandwidth of the antenna by changing the position of the capacitive loading too?
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