antenna-theory.com

[rbendel]

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

[Schubert]

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)

[rbendel]

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