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Original question:

RF430FRL152H: PCB Layout circle antenna design

RF430FRL152H: Optimizing reading range with antenna design

tina chan
Prodigy 105 points
Part Number: RF430FRL152H

Hi there.

I am trying to design a small circular antenna(around 10mm in diameter) to use with RF430FRL152H passively and I would like to optimize the reading range so it would be as long as possible. 

  1. Is there an optimum inductance when designing the antenna?
    I noticed the antenna design guide stated that the range is from 1uH to 4uH and in the transponder datasheet stated the recommend operation condition is 2.66uH. But the inductance used in RF430FRL152HEVM and temperature patch used 1.8uH for the antenna. Moreover, someone said it should be 1 - 1.5uH in one of the posts in the forum.
    May I ask what is the optimum inductance for designing antenna and does this optimum inductance vary depend on the size of the antenna?

  2. How much power can the tag harvest from the antenna? I am aware the voltage and current were stated in the "Frequently asked Questions" for VDSSW, VDD2X and VDDH. Does the current increase higher than the stated one if the reader used can produce high power or the reading distance is extremely short? 

  3. Apart from increasing the size of the antenna and tuning the resonance frequency to be at 13.56MHz by changing the external capacitator, is there anything that can be done with the antenna design or the tag to increase the reading range?

  4. If I placed the chip and other necessary components in the middle of the antenna (just like the temperature patch), does it decrease the reading range? And if the antenna is as small as 10mm in diameter that means the antenna would be closer to the components, would it affect the IC to perform?

Thanks!

  • 0
    TI__Mastermind 18265 points

    Hello Tina,

    please see the following two documents that can give you answers to most of your question.

    RF430FRL15xH FAQ (see chapter 2.4 regarding the currents):

    http://www.ti.com/lit/an/sloa247c/sloa247c.pdf

    and the document "Transponder Practical Antenna Design":

    http://www.ti.com/lit/an/sloa217a/sloa217a.pdf

    Best regards,

    Helfried

  • 0
    TI__Guru*** 135355 points

    Hello Tina,

    Just to offer a quick comment...

    tina chan said:
    Apart from increasing the size of the antenna and tuning the resonance frequency to be at 13.56MHz by changing the external capacitator, is there anything that can be done with the antenna design or the tag to increase the reading range?

    That is going to be largely dependent on the output power of the reader. A good antenna size helps promote strong coupling with the reader and resonance is very important to ensure the tag performs well but the rest is up to the power of the RF field from the reader.

  • 0 in reply to Helfried Vollbrecht
    Prodigy 105 points

    Thanks Helfried.

    So is there an optimum inductance when designing the antenna? Since I can change the number of turn or spacing to adjust the inductance.

    Is the current stated in Chapter 2.4 the maximum current that I can draw? Or does it change if I have got a high power reader?

  • 0 in reply to tina chan
    TI__Mastermind 18265 points

    Hello Tina,

    I can not give a recommendation for an optimum antenna inductance because this depends on a lot of parameters that effect the coupling between the reader and the tag. This is, for instance, the inductance and also the dimensions of the antenna. If you are using only one specific reader you should test with different tag inductance and see what gives better results.

    The currents stated for the VDDSW and the VDD2X should be seen as max. values. You can try to draw more current from the VDDH source but a max value is not specified.

    Best regards,

    Helfried