2022-04-05 10:25 AM
Hello, i designed a PCB with footprint for st25dv04k and antenna, I connected the 2 antenna port to the IC chip.
The antenna is 10mm X 50mm, 6 loops, a width of 0.15mm and 0.15mm pitch.
The antenna inductance L is 2.5uH according to tag capacitance.
I soldered the tag, fairly but it seems that I couldn't detect it with any rfid/nfc reader.
I attached the PCB picture, can you help detect what is the problem?
Solved! Go to Solution.
2022-04-08 08:23 AM
Hello,
I think your antenna is not tuned correctly: 2.4uH is too small.
The formula to calculate the antenna inductance is: La = 1/(Cs(2*pi*f)^2)
Cs is the tuning capacitance. In case of ST25DV04K it is 28.5pF as indicated in the datasheet.
f is the target resonant frequency, here 13.56MHz.
If you make the calculation, you will find that you need an antenna inductance of ~4.8uH.
(with 2.5uH you are tuned for 18.8MHz which is too high).
Please be also careful not to place ground plane under/around the antenna.
I recommend you to read those two application notes. They explain how to design an antenna and also how to test it:
You can also use the eDesignSuite tool to design your antenna: NFC Inductance | RF Design | eDesignSuite | STMicroelectronics
Best regards.
2022-04-08 08:23 AM
Hello,
I think your antenna is not tuned correctly: 2.4uH is too small.
The formula to calculate the antenna inductance is: La = 1/(Cs(2*pi*f)^2)
Cs is the tuning capacitance. In case of ST25DV04K it is 28.5pF as indicated in the datasheet.
f is the target resonant frequency, here 13.56MHz.
If you make the calculation, you will find that you need an antenna inductance of ~4.8uH.
(with 2.5uH you are tuned for 18.8MHz which is too high).
Please be also careful not to place ground plane under/around the antenna.
I recommend you to read those two application notes. They explain how to design an antenna and also how to test it:
You can also use the eDesignSuite tool to design your antenna: NFC Inductance | RF Design | eDesignSuite | STMicroelectronics
Best regards.
2022-05-03 04:05 AM
Thank you!
I designed the antenna again with the right parameters and now it works
2022-05-03 04:33 AM
Good news! I'm glad I could help 😀