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Original question:

CC2538: CC2538 high frequency emission test

CC2538: CC2538 high frequency emission test

Lin Fiske
Intellectual 690 points

Part Number: CC2538

I have followed your instruction. The emission is improved by 3 dB. However, it is still 2.5dB fail. Please tell us how to further improve it.

  • 0
    TI__Mastermind 27145 points
    Hi,

    Could you please send me your latest design ( Schematic in PDF and PCB Layout in Gerber format) for review?
    I observed lot of comments in my previous review. Did you implement all?

    Thanks,
    PM
  • 0 in reply to PM
    Intellectual 690 points

    If I increase the Rbias from 56k to 100k, the emission will be improved by 10dB. Please tell me it has negative effect by changing Rbias to 100k or not. I have try to add a 4pF cap and 10pF cap to parallel with the resisor, and the emission has no improvement. Are there any other things we can do to improve the problem

  • 0 in reply to Lin Fiske
    TI__Mastermind 27145 points
    Hi,

    Please don't change Rbias Resistor value. This Resistor sets the Bias current ( Reference) to internal circuit.
    At what Freqs you are failing and at what Tx power level?
    What are the spur Freqs?
    Could you please post a Plot of your test results?
    If you are not comfortable in posing on this Form then you can send me the Freiend Request from this forum.

    Thanks,
    PM
  • 0 in reply to PM
    Intellectual 690 points

    The zigbee IC is set at 2475 MH Rx mode. Attached please find the RE result. It fail at around 4950MHzRE_Failure.pdf

  • 0 in reply to Lin Fiske
    TI__Mastermind 27145 points
    Hi,

    It seems the LO freq (4950MHz) is leaking through. So, you need to debug to find the path for this radiation. This could radiate from the Power Supply traces or through RF Path .

    Did you do conductive measurements? If it is in conductive path then you need to improve your Harmonic filter and Antenna matching.

    Did you try with SmartRF Studio software (to control CC2538 from SmartRF Studio instead of running from the ZigBee code).

    Thanks,
    PM