Inductance of antenna used in STEVAL-D25R300A

[Hooyoung Jung]

Hello,

I am designing an NFC reader based on the ST25R300, using the STEVAL-D25R300A schematic as a reference for the antenna matching network. My board uses the same component values on each side of the differential output:

L1/L2 = 120 nH (EMC filter series)

C11/C8 = 390 pF (EMC filter shunt)

C1/C12 = 82 pF each, in parallel (series matching)

C14 = 120 pF (shunt)

C67 = 39 pF (shunt)

C59 = 10 pF, C16 = 150 pF (RFI divider)

R3/R4 = 2.2 ohm

I could not find the antenna coil parameters in the user manual or the design files. Could you please provide the following for the antenna used on STEVAL-D25R300A?

1. Coil inductance at 13.56 MHz

2. Coil AC resistance (or Q) at 13.56 MHz

3. Whether the antenna is a PCB trace coil or a discrete component, and if it is a PCB trace, the outer dimensions and number of turns

4. The target differential impedance the matching network above was designed for

 

Thank you.

[Travis Palmer]

Hello Hooyoung Jung,

Please find below the measurement of the antenna parameter. 

The antenna itself is a 66x66mm antenna with cooper etched traces. 

Please be aware that a change in the PCB layer stack can already impact those antenna parameter and therefore require a re-tuning. 

If you are copying the antenna geometry on your PCB, please ensure that the antenna parameter are the same and the resulting antenna matching is according to the application note AN6092 “Antenna design for ST25R210, ST25R300, ST25R500, and ST25R501 devices”.

BR Travis

[Hooyoung Jung]

Thank you for the reply!