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Visitor II
May 22, 2020
Solved

NFC antenna - total resistance of antenna copper traces

  • May 22, 2020
  • 2 replies
  • 1154 views

According to this values on eDesign Suite:

0693W000001pKRrQAM.png

What would be the resistance of the entire trace, from one edge to other, in ohms? NXP calculator gave result as 2,05 ohms on their tool. But I am here to ask what would be the actual resistance of the antenna above? I need to know the resistance to calculate the EMI filter and coupling components.

Can I rely on that 2,05 ohms value?

Regards.

    This topic has been closed for replies.
    Best answer by Henry Crane

    Hello,

    a simulation of your antenna leads to 2 ohms for the real part of impedance at 13.56MHz.

    By experience, this result shall be multiplied by 1.5 or 2 to fit with measurements done using network analyzer or impedance analyzer.

    best regards,

    Feel free to contact us for more information,

    Henry Crane NFC/RFID support.

    2 replies

    JPehl.1Author
    Visitor II
    May 22, 2020

    I have used some online copper trace resistance calculators and had result of around 1.6~1.65 ohms.

    parameters are:

    • thickness = 1/2oz = 18um
    • width = 0.25mm
    • length = 418mm

    I got that 1.6ohm result on 5 calculators, so it should be correct. And I will use that value on the ST25R95 filter and matching calculation.

    I just need to know the correct value to input it on the spreadsheet.

    Current layout of NFC is on right: 0693W000001pKpZQAU.png

    ST Employee
    July 28, 2020

    Hello,

    a simulation of your antenna leads to 2 ohms for the real part of impedance at 13.56MHz.

    By experience, this result shall be multiplied by 1.5 or 2 to fit with measurements done using network analyzer or impedance analyzer.

    best regards,

    Feel free to contact us for more information,

    Henry Crane NFC/RFID support.