CC110L: CC110LRGP spurious emission

Part Number: CC110L

Tool/software:

Hi Team,

CC110LRGP is used for years by my customer as an 868MHz transceiver. They are certifying a new variant of one of the end products for the first time in an official certification lab.

During testing, the lab noticed a spurious emission at 699,3MHz. They also did the tests on a completely other board that also uses the CC110L and detected the 699MHz spurious emission as well.

  • Is this coming from inside the CC110L?
  • Is this a known phenomenon? How can this be solved?

 

This is the test result of the spurious emission of the official certification lab:

Best Regards,

Madhurya

  • Hi,

    Yes, this spur at fc - 169 MHz is known and in the ref design schematic this is mentioned:

    Do you have the customer's schematic ?

  • Hi,

    Here below is our schematic of that failing product.

    They use the balun Johanson 0896BM15A0001 followed by some recommended filter components by the Johanson datasheet.

    But  have no filter as in our schematic, unless that would be integrated in the balun.

    They’ll try to put the notch filter instead of our C113 to check if it can fix the issue.

     

    From DN017 - CC11xx 868/915 MHz RF Matching:

     

    Apparently, the notch filter is only required when using an antenna connector. I find that quite strange.

    Best Regards,

    Madhurya

  • Hi,

    Looks like I missed the attachments, below is the schematics -  

    Details on Notch filter - 

    Looking forward to your feedback!

    Best Regards,

    Madhurya 

  • Hi team,

    While trying the notch filter design, my customer noticed that the filter frequency is centered around 895.3MHz, according to simulation and measurement.

    Then they  changed the inductor from 3.3nH to 5.6nH to shift the filter frequency to about 688MHz, which is close enough to 699MHz to be effective.

    Maybe your team can review our solution and/or explain why the proposed filter does not seem to be centered around 699MHz?

  • Hi Team,

    Any feedback on this topic?

    Best Regards,

    madhurya

  • There are always some layout parasitics that can effect the exact component values. If 5.6 nH is providing a notch at 688 MHz then recommend to use this value.