Some Clarification on the NFC Antenna Design Guide PPT

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Some Clarification on the NFC Antenna Design Guide PPT

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nddpd
Contributor I

Hi All,

I'm working on a new project that will be using NFC technology. I found the design guide very helpful, but I'd like to have a few things clarified. The presentation can be found here:

http://www.themobileknowledge.com/sites/default/files/NFC%20Reader%20Design%20II%20-%20Antenna%20des...

Can someone explain the coupling coefficient k? The value seems very vague and I'm having trouble understanding what it represents. It makes the charts on pages 14 and 15 a little challenging to interpret.

Also, if someone could interpret the two charts on pages 14 and 15, it would be extremely helpful.

On page 14, r = x. Does this mean that the read range is approximately equal to the radius of the antenna (assuming a flat circular coil)? Or does this mean the radius of the magnetic field produced by coil?

Does the coil need to be flat like in a smart phone? Is it possible to design comparable antennas that are curved or dome-like? As long as the magnetic field is the same?

Essentially, I'd like to understand the size limitations in antenna design as I will be trying to implement an antenna into a new design

Thanks for your help!

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Jorge_Gonzalez
NXP Employee
NXP Employee

Hello Donovan Deame,

In regards to your antenna questions:

The coupling coefficient k is explained in more detail in the NFC antenna webinars, e.g. the number 1:

http://www.nxp.com/support/online-academy/which-antenna-for-what-purpose-nfc-reader-antenna-design-1...

There is a series of antenna design recorded webinar sessions, here:

http://www.nxp.com/support/classroom-training-events/webinars-archive:WEBINARS-ARCHIVE?fsrch=1&sr=1&...

About r = x: yes, the optimum coupling at a certain distance x is given, if the antenna coil radius is equal to the distance.

Other antenna form factors are possible, even though not optimum.

Regards!

Jorge Gonzalez