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CC3301: CC3301 band edge emissions

Juha Hämäläinen
Prodigy 50 points

Part Number: CC3301

We are FCC testing a gateway device with CC3301 radio, TDK DEA162450BT-1295A1 filter, and a custom PCB trace antenna, STM32U5 microcontroller running FreeRTOS and your SDK version 7. The cc33xx_fw.bin is all defaults. Now the testing lab said, that the band edge emissions at 2483.5-2500 MHz are excessive when the radio is transmitting on channel 11 at 20 dBm. We are forced to lower the TX power by 5 dB, maybe even more to have some margin.

A poor PCB design could cause harmonics, but the band edge issues are typically more up to the radio IC itself. I viewed your test report FR482308B_R02 on CC3301MOD and found that there are several band edge test results with less than 1 dB margin! 

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Is this really the case that your radio has that wide emissions? Is there anything we can do, except to lower the TX power? We wouldn't have chosen this radio if we knew this.

  • +1
    Expert 1931 points

    What conf.bin, exactly, are  you using?

    I'm not sure what you're expecting, but reduced power on the band edge channels is standard for regulatory compliance in the US. Band edge channels will always be lower power than interior channels in the US, unless you are intentionally giving up power on the interior channels.

  • 0 in reply to Dean Ramsier
    Prodigy 50 points

    Okay I didn't know that it is a standard practice to have lower power at the outermost channels, this is our first Wi-Fi project. After your message I was able to confirm that you are right. So we will use the PowerLimitArray parameters in the configuration file to adjust the powers. So far we used the default conf.bin delivered in your SDK as I said in my opening message.

  • 0 in reply to Juha Hämäläinen
    TI__Mastermind 48005 points

    Hey Dean,

    Thanks for the assist here.

    Hi Juha,

    On top of the PLA, I suggest also setting RegDomain setting to FCC which should also add some filtering on CH1/11 to better optimize BE emissions.