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TRF7970A: TRF7970A Evaluation Module Antenna Gain

David Holland
Prodigy 30 points
Part Number: TRF7970A

We created an RFID board based on the TRF7970A module based on the TRF7960TB module (SLOU297.pdf page 6).  

For testing in Japan, we have a request for the Antenna gain for the PCB loop antenna in the reference design.

Is there an equation to calculate the loop antenna gain from the PCB layout and component values at 13.56MHZ?

  • 0
    TI__Guru*** 133215 points
    Hello David,

    I don't know of any equations for that, they may exist but it's not something we do. For antenna gain, that could probably measured using a network analyzer?

    Our concerns with antenna design are on the matching of the antenna to the 50 ohm TRF79xx match network (affects gain as a poor match will reduce the power transfer from reader and thus hurt the gain) and the Q factor of the antenna which impacts read range for tag technologies.

    What is the background for the request for testing purposes? If it's for some sort of FCC/RED kind of compliance I can check about what we reported when going through testing last year for the new EU standards.
  • 0 in reply to Ralph Jacobi
    Prodigy 30 points
    The request is specific to Article 19 testing in Japan. The Japan questionnaire asks for Antenna Gain and lists the question as Mandatory.
    I'm looking for a general gain for a loop with dimensions 2.3 x 3.5 cm with 3 turns of 0.635mm (25mil) traces on FR4 material matched to a 50ohm network. The circuit is identical to the one in the Ti document I referenced above (www.ti.com/lit/ug/slou297/slou297.pdf)
  • 0 in reply to David Holland
    TI__Guru*** 133215 points
    Hello David,

    Thanks for the background. Here is the feedback I got back: "Since a magnetic field antenna does not really have any gain, this should be listed as gain=1 or gain=0dB."