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ANTENNA FERRITE SHIELDING

 
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rbendel
Antenna-Theory.com Newbie


Joined: 19 May 2014
Posts: 4
Location: France

PostPosted: Mon May 19, 2014 3:23 pm    Post subject: ANTENNA FERRITE SHIELDING Reply with quote

Hello
I found in an application note:
"The benefit of a ferrite is to shield an antenna against the influence of metal (ex: housing of the reader, PCB ground,...)".

I wonder how does it work. Because i read that ferrite reduces eddy currents (power dissipation) from metal piece but doesn't prevent from detuning.

Is it true? Then how could it "really" shield the antenna (basic principles)?

Is ferrite what we call Perfect Magnetic Conductor (PMC: H//=0, En=0)?

Thanks a lot
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Schubert
Antenna Wizard


Joined: 08 Apr 2009
Posts: 161

PostPosted: Mon May 19, 2014 11:23 pm    Post subject: Reply with quote

Shielding is not the right word.

This only applies for NFC antennas (near field antennas that aren't really antennas). The ferrite increases the "effective separation" to the metal behind the coil (by using a very high permeability material). This enables a thinner antenna (i.e. a coil closer to a metal surface)
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rbendel
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Joined: 19 May 2014
Posts: 4
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PostPosted: Tue May 20, 2014 6:55 am    Post subject: Reply with quote

thanks a lot for the reply.
Do you know where i could find some more explanations (litterature, application note...)?
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