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Dilip
Visitor II
September 10, 2025
Solved

ST25R3916B read range for ISO14443A tag

  • September 10, 2025
  • 1 reply
  • 602 views

Hi ST team , 

I have designed NFC reader using ST25R3916B  with single ended antenna connected with cable. Antenna is on different PCB. I would like to read ISO1443A tags using this antenna and want to have read range of around 5 cm. Right now when i am able to read the tags but with no range, i need to touch the tag on antenna. Pls help me to tune my matching circuit on reader side and on antenna side. I am attaching here reader schematic, antenna schematic , antenna PCB. Let me know what component value should i choose to get that range. Also I dont have VNA , so i am not able measure antenna parameters and not able to use ST antenna matching tool, so pls provide me the best component values to based on the schematics

Reader side

Dilip_0-1757470139327.png

Antenna side

Dilip_1-1757470221757.png

Antenna PCB - 4 turns, 50mm x 50mm square, track width = 0.152mm,  track spacing  =  0.2mm

Dilip_2-1757470382375.png

 

Regards

Dilip Motwani

 

 

    This topic has been closed for replies.
    Best answer by Travis Palmer

    Hi Dilip,

     

    the antenna you are showing seems to be matched for 50Ohm.

    You can try to follow the following AN:

    https://www.st.com/resource/en/application_note/an5592-st25r-single-ended-antenna-matching-stmicroelectronics.pdf

    If the antenna is self-made and needs to be tuned to 50Ohm you might require a VNA.

    Also for verification a VNA is very helpful. There are other threads in the community where people are using a nanoVNA device which seems to work reliable.

    BR Travis 

    1 reply

    U
    Ulysses HERNIOSUS
    Technical Moderator
    September 10, 2025

    Hi,

    being more on the software side but typically it will not be possible to match and antenna without tools.

    The ST antenna matching tool is freely available as STSW-ST25R004 or as eDesignSuite available from the product page https://www.st.com/en/nfc/st25r3916b.html#overview. There are various app notes (AN5276 for the chip that you are using) which guide through the antenna matching.

    To my knowledge also a VNA is essential. Also low-cost ones in the below $500 range are typically usable for this use case (miniVNA, nanoVNA, .......)

    BR, Ulysses

    D
    DilipAuthor
    Visitor II
    September 10, 2025

    Hi Ulysses

    Anyone from HW team can help here if possible. I understand VNA is required  but I don't have that so I am asking for the value of the components.

    Dilip

     

    U
    Ulysses HERNIOSUS
    Technical Moderator
    September 10, 2025

    Hi Dilip,

    just had a chat with HW colleague: What you are asking is not possible. 

    You can try to put your antenna into eDesignSuite and use then the matching tool to generate some component values. However expectation is that this is still considerably far from reality and needs to be tuned using VNA.

    Sorry, cannot help more. Ulysses

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