Development Kits antenna considerations

Gaston · ‎2020-10-30

Hi,

I've noticed that the pcb antenna (ANT300) on ST25R3916-DISCO has the 3rd pin unconnected. The X-NUCLEO-NFC06A1 has this 3rd pin tied to GND. On the other hand, an identical antenna (same dimension and turns that previous one) on X-NUCLEO-NFC05A1 has only 2 pins so there is no 3rd pin tied to GND nor left unconnected (High-z)

What is the reason for these differences in the evaluation boards with the same application?

regards,

gaston

Travis Palmer · ‎2020-11-02

Hello Gaston,

You are right. Comparing for example the NFC05A1 and NFC06A1 antenna, they look very similar but are not the same. They have same number of turns, antenna track width and dimension.

The NFC05A1 antenna was chosen based on previous boards (e.g. NFC03A1).

On the NFC06A1, we changed to a symmetric antenna with center tap which can be connected to GND. This center tap is in the middle of the electrical length of the antenna. If the antenna is symmetric, the center tap or virtual GND can either be left open or connected to GND. it does not affect the antenna parameters or its performance.

BR Travis

View solution in original post

Travis Palmer · ‎2020-11-02

Hello Gaston,

You are right. Comparing for example the NFC05A1 and NFC06A1 antenna, they look very similar but are not the same. They have same number of turns, antenna track width and dimension.

The NFC05A1 antenna was chosen based on previous boards (e.g. NFC03A1).

On the NFC06A1, we changed to a symmetric antenna with center tap which can be connected to GND. This center tap is in the middle of the electrical length of the antenna. If the antenna is symmetric, the center tap or virtual GND can either be left open or connected to GND. it does not affect the antenna parameters or its performance.

BR Travis