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CC1312R: spurious

TSUDA SHOGO
Prodigy 50 points
Part Number: CC1312R

Tool/software:

I am using CC1312R to develop products using 920MHz and 1200MHz frequencies.

However, the overall noise floor at 920 MHz is high and spurious around the carrier wave does not meet the standard.

The 1200 MHz band also fails to meet spurious standards in the neighboring bands.

Although IIR filters, PLLs, etc. are being studied by changing values from registers, it is necessary to sacrifice ACP in order to meet the spurious standard, and the situation is such that only one of the two standards, either spurious or ACP, can be met.

[QUESTIONS]

・The CC1312R itself seems to have a higher noise floor overall, but is this what this RFIC is like?

・Since the noise floor around the carrier wave is high, is there any way to set up a filter or register that can drop spurious in this area?

  • 0
    TI__Expert 3630 points

    Hi Tsuda,

    Can you share spectrum analyzer plots showing the ACP and spurious emissions?

  • 0 in reply to Diego P
    Prodigy 50 points

    Hi Diego P.

    Thanks for getting back to me.

    Shows images of actual measured spurious in the 920 MHz/1200 MHz band.

    920MHz.zip

    1216MHz.zip

    [About 920MHz]

    ・The spurious in the neighbor band is too large to meet the standard value of -36 dBm. (Compliant with STD-T108)

    [About 1200MHz]

    ・The spurious in the near band is too large to meet the standard value of -26dBm. (STD-T67 compliant)

  • 0 in reply to TSUDA SHOGO
    TI__Genius 12885 points

    Hi Tsuda,

    It is probably best to work on resolving the 920 MHz issues first. Please can you share the settings you are using (ideally exported from SmartRF Studio)?

    Regards,

    Zack

  • 0 in reply to ZC
    Prodigy 50 points

    Hi Diego P.

    We will send you a program of set values for transmitting 920 MHz radio waves.

    If you have a filter that can lower the spurious in the near band, I would like to know the register value.

    Thank you for your cooperation.

    920MHz_settings .zip

  • 0 in reply to TSUDA SHOGO
    Prodigy 50 points

    Sorry for the series of posts.
    I would like to confirm something additional.

    On the evaluation board,
    As shown in the figure below, the transmit spur has a level of -55.44 [dBm] at a transmit frequency of +48 [MHz].
    The provisions of the Radio Law are -55 [dBm] or less, and there is no margin for the standard.
    Could you please advise how to resolve this issue, including this information?

  • 0 in reply to TSUDA SHOGO
    TI__Expert 3630 points

    Hi Tsuda,

    question for the ACP. Currently, you have a 40 kHz deviation. is it possible to reduce the deviation, or do you need to support communication with another device that is using that deviation?

  • 0 in reply to Diego P
    Prodigy 50 points

    Hi,Diego P.

    Deviation would like to solve the problem without changing from 40 kHz. I also want to resolve the matter I asked about earlier on 27 September. Is there any solution to the problem? Although it is urgent, we would like to receive an answer by the end of 1 Oct on this matter.

    ⇒[On the evaluation board,
    As shown in the figure below, the transmit spur has a level of -55.44 [dBm] at a transmit frequency of +48 [MHz].
    The provisions of the Radio Law are -55 [dBm] or less, and there is no margin for the standard.
    Could you please advise how to resolve this issue, including this information?]

    Thank you for your cooperation.

  • 0 in reply to TSUDA SHOGO
    TI__Expert 3630 points

    Hi Tsuda,

    Are you using external load capacitors for crystal? To meet ARIB standards we recommend having the external load capacitors to reduce the 48 MHz spur you are seeing.

    From section 3.1.1 of CC13xx/CC26xx Hardware Configuration and PCB Design Considerations app note

    https://www.tij.co.jp/jp/lit/an/swra640h/swra640h.pdf

    The errata also mentions this:

  • 0 in reply to Diego P
    Prodigy 50 points

    Hi Diego P.

    The TCXO load capacitor is used. After re-adjustment, a margin of 2.5 dB was obtained compared to the standard of -55 dBm. Although there is no margin against the standard, we are considering proceeding with this study.
    Thank you very much.

    If there is any method that can suppress spurious in the neighbouring bands, please let us know.

    Thank you for your cooperation.