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LP-CC2651P3: FCC certification (channel 26)

Andy Pozsgay
Intellectual 260 points
Part Number: LP-CC2651P3
Other Parts Discussed in Thread: CC2651P3, , CC2651R3SIPA, CC2652PSIP, CC2651R3, LAUNCHXL-CC26X2R1, CC2652R

We performed FCC pre-compliance testing today with our design that contains CC2651RKP. Our design supports a maximum output power of +8.5dBm. At this level, we are failing 15.205 by 17dB at 2483.5 MHz.

We also looked at a LP-CC2651P3 set to +20dBm output. It is failing by 26dB. We then reduced the output of the LP_CC2651P3 and found we needed to set the output to -8dBm or lower to pass. This output level makes channel 26 unusable from a practical perspective.

According to the "TI 15.4 Stack User's Guide", the max output on channel 26 for LP_CC2651R3SIPA is +1dBm. There is no entry listed for LP_CC2651P3. Is it expected that the channel 26 max output for LP_CC2651P3 would be -8dBm?

Regards,
Andy

  • 0
    TI__Guru**** 208857 points

    Hi Andy,

    I believe you are referring to the FCC Certification Considerations section of the TI 15.4-Stack User's Guide.  The maximum expected output power for the LP_CC2652PSIP at channel 26 would be +2 dBm.  This is also reflected in mac_user_config.c comments for the PowerLimitTableIeee array.  As noted in documentation, power limitation values will vary slightly for each custom hardware design, thus caution should be taken to identify the optimal values during FCC certification and modify the table accordingly.

    Regards,
    Ryan

  • 0 in reply to Ryan Brown1
    Intellectual 260 points

    Hi Ryan,

    Are you saying that the LP_CC2652PSIP and LP_CC2651P3 have the same expected output power at channel 26? Based on the results from our FCC test lab, the LP_CC2651P3 certainly would NOT be compliant at +2 dBm output. The maximum output power at channel 26 for LP_CC2651P3 is -8 dBm. (See my original post for details.)

    Regards,
    Andy

  • 0 in reply to Andy Pozsgay
    TI__Guru**** 208857 points

    I apologize for the confusion, I meant to say that "The maximum expected output power for the LP_CC2651P3 at channel 26 would be +1 dBm". Can you please share more information about your test setup and the observed results which indicate failure on a LP-CC2651P3?  I will ask the SimpleLink hardware experts to comment but please be patient as they are on leave until January 3rd.

    Regards,
    Ryan

  • 0
    TI__Expert 6320 points

    Hi Andy,

    at +5dBm and below the LP_CC2651P3 and LP_CC2651R3 use the same RF path and otherwise are internally the same so should operate the same. Therefor the limit should be +1dBm for both.

    Did you have any more information on the issue as Ryan had requested?

    Jake

  • 0 in reply to Jake Pulliam
    Intellectual 260 points

    Hi Jake,

    We setup a LP_CC2651P3 on channel 26 at +20dBm. Our lab measured 79.9 dBuV/m at 2483.5 MHz. The FCC limit is 54 dBuV/m. We needed to set the output power to -8dBm to get under the 54 dBuV/m limit.

    Do you have any test data from the LP_CC2651R3 you can provide?

    Thanks,
    Andy

  • 0 in reply to Andy Pozsgay
    TI__Expert 6320 points

    Hi Andy,

    I'm seeing what was done and what can be shared. I'll follow-up by 5PM CST on Monday.

    Thanks,

    Jake

  • 0 in reply to Andy Pozsgay
    TI__Expert 6320 points

    Hi Andy,

    I looked into it and I don't have any FCC equivalent test data for the launchpad. It's not necessarily something that we'd typically do since it's evaluation hardware only.

    I discussed with some other folks and from my understanding it's not always feasible to meet FCC requirements when using channel 26 at higher power levels. There is some clarification from the FCC on the test methodology and the band-edge. See FCC DA 00-705 (Marker-Delta method on the last page) which may give a little more margin (unless that method is already used in your pre-compliance testing) see this app-note for an example  of the method https://www.ti.com/lit/an/swra465a/swra465a.pdf .

    Thanks,

    Jake

  • 0 in reply to Jake Pulliam
    Intellectual 260 points

    Hi Jake,

    Thank you for the details on the marker-delta method. I'm not sure if our lab used that method, but I will look into it.

    If TI did not make the band-edge measurement, how was it determined that the maximum output level on channel 26 is +1dBm for compliance?

    Regards,
    Andy

  • 0 in reply to Andy Pozsgay
    TI__Expert 6320 points

    Hey Andy,

    Let me reset the discussion a little bit and make sure we're on the same page. What Ryan had originally linked and I think you were referring to (please correct me if I'm wrong) was the FCC compliance page within the SDK documentation found here, that's referring to a specific set of Launchpads and an issue meeting FCC limits at the 2nd harmonic. This is way out of range of what you're talking about failing at 2883.5 MHz, which is the band-edge. I think these two different issues got mixed together here.

    I also mixed up some part numbers above. There isn't an LP_CC2651R3. For evaluation there's the equivalent CC2652R launchpad, the LAUNCHXL-CC26X2R1. We would have measurement data for parts using engineering hardware but not necessarily every part would be placed on a Launchpad for customer evaluation. If parts are similar enough, then only one part from a family would be released for evaluation.

    Otherwise, I think I addressed the band-edge issue above.

    Thanks,

    Jake

  • 0 in reply to Jake Pulliam
    Intellectual 260 points

    Hi Jake,

    Yes, when I initially reported that we had an issue at band-edge (2483.5 MHz), Ryan pointed me to the SDK document that listed the channel 26 power limits for various launchpads.

    By 2nd harmonic, are you referring to 4.96GHz? In our testing we did see emissions there but it was below the limit.

    Regards,
    Andy

  • +1 in reply to Andy Pozsgay
    TI__Expert 6320 points

    Yes, 2nd harmonic at 4.96GHz. So that section of the SDK documentation is not related to your issue. It's specific to the devices listed and the 2nd harmonic.

    For band-edge, depending on what you end up measuring based on the notes provided above, channel 26 may not be useful for your application. At least depending on how much you have to back off on power or duty cycle at that channel.

    Thanks,

    Jake