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gte938x
Visitor II
December 22, 2023
Solved

ST25R3916 radiated emission issue

  • December 22, 2023
  • 1 reply
  • 1510 views

Hi,

The FCC test report can be found here: https://fccid.io/YCPNFC06A1/Test-Report/Test-Report-4494604.pdf.

We are running X-NUCLEO-NFC06A1 stack on top of NUCLEO-L476RG board with STM X-CUBE-NFC6 demo software, and the emission scan (at Intertek) is something like this (see below). We cannot replicate the same result in the above FCC report.

gte938x_0-1703256576837.png

On page 8 of the test report (EUT Radio Specifications), Transmitter Parameters section (b) lists many different modulation types. Then it says "A test mode allow to test all modulations at the same time".

I am wondering if this means the test mode was running with a different firmware. We are running  X-CUBE-NFC6 software tools from https://www.st.com/en/ecosystems/x-nucleo-nfc06a1.html#tools-software, and I do not think it allows testing all modulations at the same time.

Modulation differences should lead to different emission peak levels. For example, in NFC type A, Miller encoding (delay encoding) is used with an amplitude modulation at 100%, while in NFC type B, Manchester encoding is used with amplitude modulation only at 10%. The two different types of modulations have different peak levels.

In the 30MHz to 1GHz scan data (after page 40), there are multiples adjacent peaks in the band of upper 60MHz to 70MHz (a few are even in 80MHz) range, what are these peaks representing? They are not the harmonics of NFC carrier, and most importantly, we do not see this kind of "wide" band peaks during our test.

Also, on page 17, it describes the test method, why STM has to do peak measurement and quasi-peak measurement at different setups (3-meter in chamber vs 10-meter open area). To me, if it is an easy pass, it does not make sense to contribute extra labor and equipment to do testing at these level of complicated different setups. Quasi-peak measurement can run immediately after peak scan under the same setup at most test labs.

Thanks.

Lu Dong

 

 

 

    This topic has been closed for replies.
    Best answer by Alan BST

    Hello,

     

    Sorry for the late answer,

    The certification tests are not done directly by STMicroelectronics. We rely on an external accredited laboratory for those, because the results are very dependent on the environment (antenna used, anechoic chamber dimension, distance between the system and the antenna…), which needs to follow the FCC requirements. In addition, it is always a complete system which is tested as a reader cannot be tested alone. The system includes the reader but also tags, the power supply, the cables…that can all influence the results (in the past, we saw issues with some power supply)

    Hence it is very difficult to explain the differences with your results as different configurations can lead to different results. 

     

    Regards

    Alan

    1 reply

    A
    Alan BSTAnswer
    ST Employee
    February 29, 2024

    Hello,

     

    Sorry for the late answer,

    The certification tests are not done directly by STMicroelectronics. We rely on an external accredited laboratory for those, because the results are very dependent on the environment (antenna used, anechoic chamber dimension, distance between the system and the antenna…), which needs to follow the FCC requirements. In addition, it is always a complete system which is tested as a reader cannot be tested alone. The system includes the reader but also tags, the power supply, the cables…that can all influence the results (in the past, we saw issues with some power supply)

    Hence it is very difficult to explain the differences with your results as different configurations can lead to different results. 

     

    Regards

    Alan

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