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TRF7970A: Does shape or size of an antenna effect it's performance.

Abhyuday Reddy Chada
Prodigy 40 points
Part Number: TRF7970A


We designed a rectangular antenna which worked fine for our application but physically it had to be revised so, we designed a circular antenna to meet our requirements with the same inductance and a smaller coil compared to the rectangular antenna. So, my question is does the shape of the antenna matter or is it the size? If it is the size, will increasing the inductance enhance it's strength?

  • 0
    TI__Mastermind 24890 points

    Hello Abhyuday,

    I think in your case the shape does not matter, but the reduced size. It can be illustrated with a solar panel: the bigger the solar panel, the more energy can be harvested.

    Another aspect would be the distance of the coil windings, but this impacts the inductance, and you said the new antenna is matching to the targeted inductance.

    You can have a look to the Antenna Design Guide (https://www.ti.com/lit/pdf/sloa241) for further details.

    Best regards,

    Andreas.

  • 0 in reply to Andreas Mueller
    Prodigy 40 points

    Hello Andreas,

    So, we have tested an antenna from Molex with the dimensions of 2.6cmx2.4cm which is small compared to our circular antenna, we measured the inductance of 5.4uH which way out of what is recommended in the design guide but, the antenna had a better strength than the circular one we designed. So, my question is does increasing the inductance improve the strength for smaller antennas?

    Regards

    Abhyuday

  • +1
    TI__Mastermind 24890 points

    Hello Abhyuday,

    I think the inductance should have almost no influence to the coupling strength. The inductance is rather relevant for antenna tuning, which is of cause the most important aspect  for read performance. Did you always tune the antennas to 50 Ohm?

    The Q factor could also have an impact to the read performance. If your circular antenna is made from a thinner wire or PCB trace, then the resistance is higher, which leads to a lower Q factor. The Q factor should be between 7 and 10 for the most applications.

    Best regards,

    Andreas.

  • 0
    TI__Mastermind 24890 points

    Hi,

    I haven’t heard back from you for a while, so I will close this tread. If you wish to continue the discussion, please post a reply with an update below (or create a new thread).

    Best Regards,
    Andreas.