Class 3 antenna design guide

[Neel Shah]

Hello,

We referred to https://www.nxp.com/docs/en/application-note/AN10841.pdf for designing a circular NFC Class 3 antenna but information is only provided for Class 1 and Class 2 antennas in rectangular form factor.

Can you please direct us to the design guidelines for the circular form factor?

Thanks

Neel.

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[TapLinx Support]

Hi Neel,

For MIFARE Plus EV1 Class 3 antennas we don´t have design files/guidelines available.
But you can use the calculation sheet for round antennas (an Excel file) out of the NTAG Antenna design guide from this link:

https://www.nxp.com/docs/en/application-note/AN11276.zip

The TapLinx team

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[Carla Tuck]

The inductance should be measured without any matching components(should be disconnected from chip also). After the inductance of the coil alone is determined, then use the formula for resonant frequency to determine the required C value.
If the inductance is too low and does not provide resonance at ~13.56MHz using the internal capacitor.can you explain me little bit
In regards to my statement about inductance too low or high, let me explain.
If inductance is too high, lets say 4.5uH for example, it is not possible to resonate at 13.56MHz. The closest you could get would be ~12.68MHz, since we have 35pF internal capacitance. Formula is 1 / 2pi*sqrt LC. Adding external capacitance will bring down the resonant frequency, so the only way to tune this to proper resonance is by decreasing the inductance(remove turns and/or make the traces thicker).

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[Joao Garcia]

"use a fórmula da frequência ressonante para determinar o valor C " consigo medir isso via applicativo ANDROID?

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[TapLinx Support]

Hi Joao,

You cannot measure any antenna parameter from Android. The NFC interface available in Android can only be used “as it is”.

The TapLinx team

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