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CC1310: FCC regulations for Sub-GHz products

Part Number: CC1310
Other Parts Discussed in Thread: CC1190

Hi,

We build devices based on CC1310 and recently obtained FCC certification for the same. I have a question regarding the two different methods that FCC allows under Section 15.247.

In the document "GUIDANCE FOR COMPLIANCE MEASUREMENTS ON DIGITAL TRANSMISSION SYSTEM, FREQUENCY HOPPING SPREAD SPECTRUM SYSTEM, AND HYBRID SYSTEM DEVICES OPERATING UNDER SECTION 15.247 OF THE FCC RULESwe find the following statement "Equipment certified under Section 15.247 can operate as either a Digital Transmission System (DTS), Frequency Hopping Spread Spectrum (FHSS) system or a Hybrid system, as long as the appropriate requirements for each classification are met. For instance, for a device using digital modulation and frequency hopping, compliance demonstration for both the FHSS requirements and the DTS requirements is not needed. Instead, such a device could be certified by complying with either all the FHSS requirements, or all of the DTS requirements, or all of the hybrid system requirements."

The current FCC certification that we have obtained for our devices is to operate as a digital transmission system. I wanted to check if it would violate the regulations if we use a firmware based on frequency hopping. The certification lab is suggesting that and charging us more to test the devices also for the FHSS operation. However, based on the above document, it seems that we do not have to show compliance with both requirements. 

It would be great if someone can help us with this so that we don't get charged two times. Also, what is a hybrid system? I have attached the document.GetAttachment.html.pdf

Thanks in advance, 

MM

  • Hi,

    We will look into it and get ack to you ASAP. Please bear with us.

    Thanks,

    PM

  • Thanks a lot. Much appreciated.

  • Hi,

    "Equipment certified under Section 15.247 can operate as either a Digital Transmission System (DTS), Frequency Hopping Spread Spectrum (FHSS) system or a Hybrid system, as long as the appropriate requirements for each classification are met. For instance, for a device using digital modulation and frequency hopping, compliance demonstration for both the FHSS requirements and the DTS requirements is not needed. Instead, such a device could be certified by complying with either all the FHSS requirements, or all of the DTS requirements, or all of the hybrid system requirements."


    As per the 1st sentence in the above statement, the appropriate requirements ( for both FHSS and DTS) must be met. That means both modes (FHSS and DTS) must be tested to show that in both modes the DUT meets the requirements.

    But the 2nd sentence might be related to the unwanted emissions and other EMI/EMC & Safety tests. If it passes these tests in one mode (for example in DTS) and the same tests may not be required to repeat on other (FHSS) mode.

    Please note that the Manufacturer is responsible to make sure that the DUT has met all the compliance requirements before placing the equipment in the field. So, we recommend to get the advice from the 2nd Certification Lab because they are more knowledgeable in the certification matters.

    Thanks,

    PM

     

  • Hi,

    Thanks a lot for the information. Looks like we need to contact the certification lab to get more specifics. 

    Currently, we had the following attached certificate. We wanted to use the 2.5kpbs setting in the firmware with channel hopping for long-range communication. So I was wondering if we need to recertify or we can use the devices without issue.

    Best regards,

    MM

    391212CERTCAB(2AT8M-VW-S1-V2X1 01).pdf

  • Hi,

    DTS is a Wideband modulation and you are FHSS for narrowband mode. So, better to get the certification for both modes.

    Yes, please contact the Certification Lab to get more clarity on this.

    Thanks,

    PM

  • Thanks for clarifying,

    It would, unfortunately, doubles the cost given that they tested out and issued DTS already.

    At this point, the lab asked us to repeat CE and FCC tests with the narrow band FHSS since the current certificates that they issued are for DTS broadband. 

    Any way to avoid retesting? If both modes require separate testing anyways then we are out of luck. 

    Best regards,
    MM

  • Hi,

    Please consult your certification lab.

    Some common tests ( EMI and Safety) may not be required to repeat on both operating modes. You may save at least some cost.

    Thanks,

    PM

  • Thank you. 

    Checking out with the lab. I really appreciate your input. Would come back if it raises some more questions.

    Best regards,
    MM 

  • Hi,

    We just received the report for CC1310-1190 based products from the FCC lab. We failed the test when using DTS mode (WB-DSSS, 240kbps SmartRF setting).

    To be specific, the Power SpectralDensity test that failed. We had set the 26dbm with the PA and LNA set from the SmartRF setting. Please see the image for the values that failed. 

    Can someone help why that failed and how it can be remedied? The peak output power is around 25dbm. Much below the 30dbm limit.

    Best,
    MM

  • Hi,

    You have to back off power in the CC1190 to pass 8dBm in 3kHz PSD spec.

    CC1310 is not tested with front end PA.

    Please see the app note:

    http://www.ti.com/lit/an/swra591/swra591.pdf

    Regards,

  • Hi,

    That is what the lab mentioned. Can you help us by how much we should reduce the transmission power? Clearly 26dbm setting on the SmartRF Studio is quite high. Unfortunately, we would not be able to see the long-range communication.

    Another separate question is if we would see the same test fail if we repeat the FHSS test with 2.5kbps setting and 26dbm transmission power?

    Best,

    MM

  • Hi,

    Sorry for late reply.

    You should back off power until you pass 8dBm in 3kHz requirement. This impact the range.

    See this range estimator tool to see the potential range of the link. http://www.ti.com/tool/RF-RANGE-ESTIMATOR

    I have requested a colleague to guide in FHSS case.

    Regards,

  • Hi,

    The following is the table for Frequency Hopping Specs.

    FHSS equipment classified under 15.247 shall have hop channel frequencies separated by whichever is largest of 25kHz or the 20dB bandwidth of the hop channel. At least 15 non overlapping channels shall be used, and hop frequencies shall be selected in a pseudorandom order. Every channel shall be used equally on average, and the average dwell time shall not exceed 0.4 seconds within a period of 0.4 seconds times the number of channels. FHSS systems with less than 75 hop channels can employ intelligent hopping, e.g. adaptive frequency hopping.

    SRD equipment used in the 2.4 GHz band that does not fall within the 15.247 definition is classified under section 15.249.

    Thanks,

    PM