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RF430FRL152HEVM: Communication distance difference between power over RF mode and USB mode.

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Replies: 4

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Part Number: RF430FRL152HEVM

Hello,

We measured the communication distance of RF430FRL152H EVM with below conditions.

1) Antenna : Default on board antenna
     N:6, w: 37mm, h: 19mm

2) Power supply:
     - Powered by RF
     - Powered by Usb

3) ISO15693 Reader
     - TR3-LD003GW4LM-L  (4W output) 
     - TR3-LA101W4 (420 x 297 mm)

4) maximum communication distance
     - Powered by RF : 330mm
     - Powered by Usb : 350mm 


The difference between the two was smaller than I expected.
I hoped the maximum distance of usb tag is up to 50cm or more, but only 2cm difference.

According to the RF signals monitored by oscilloscope, the tag doesn't send a response to the reader at outside the maximum distance.
It seems the tag cannot receive(demodulate) the reader signal in spite of sufficient power by usb.  

[Question]

Is it possible to lengthen the distance without changing the antenna size?
I know that if we use bigger and more coiled antenna we can do it.
For example, in case of ISO15693 card (ID-1 sized antenna) the maximum distance becomes up to 70cm.

I'd like to know whether or not it is possible to lengthen theoretically even though using a small antenna.

Best regards,
Takashi Suzuki  

  • Hello Takashi-san,

    The only two ways to increase the read range based on what you describe is to either change the antenna size or increase the output power of the reader. The distances you are getting are already very impressive, more than I've ever heard the device of being capable of achieving by anyone else. To meet your goal of 50cm, I think increasing the antenna size is your best bet.

    Best Regards,

    Ralph Jacobi

  • In reply to Ralph Jacobi:

    Hi Ralph,

    Thanks a lot for your quick reply.
    Let me ask one more question just for the clarification.

    Communication error is caused by two reason generally.
    1) Tag cannot receive a command from reader.
    2) Reader cannot recive a response from tag. 

    This time No.1 is the case and,
    With the reference small antenna, the tag cannot demodulate the reader signal and no way to solve it other than increasing the antenna size, am I right?

    We are using the maximum power reader under the Japanese radio law so it is impossible to increase the reader power.
    Thanks in advance.

    Regards,
    Takashi Suzuki

  • In reply to user5364999:

    Hello Takashi-san,

    Given the tag is USB powered so there is no concern about the RF field powering the tag, then what it sounds like to me is that the RF field at the limit of the read range becomes too small for either A) the tag to register the command sent to it, or B) as you stated, for the tag to be able to load modulate the RF field in a manner that the reader can recognize the response.

    In either case, increasing the antenna size should help with this as it would improve the coupling between the tag coil and reader coil, thereby increasing the power transferred and offering a stronger signal.

    However, I must forewarn that I have doubts only increasing the coil size will be sufficient to reach a read distance of 50 cm or more. Increasing the coil size would need to improve performance by 50% with the same output power and that sounds to me difficult to achieve.

    Lastly I want to leave these comments for your understanding: The device you are using, while it is ISO15693 compliant in terms of protocol, was never intended to be used at such large read ranges. All practical applications we envisioned were for 10cm or less, and no testing occurred to determine the performance at extreme ranges such as 30-50 cm. If you find that the device is not able to meet your requirement for 50 cm read range then the only options will be to either reduce the requirement (which is exceptionally high from all my NFC experience...) or select a different tag which may offer better performance (you may find better performance with static tags that are more suited to such an application, rather than a smart tag which is an Sensor MCU first and RFID chip second).

    Best Regards,

    Ralph Jacobi

  • In reply to Ralph Jacobi:

    Hi Ralph,

    Again thanks a lot for your kind and detailed answer.
    I understood.

    Best regards,
    Takashi Suzuki

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