• State
  • Locked Locked
  • Replies 2 replies
  • Subscribers 55 subscribers
  • Views 302 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

CC1354P10: Close in Frequency Spurs ( 1.6khz spacing) being produced adjacent to carrier

Ed CURRIE
Prodigy 40 points
Part Number: CC1354P10

Hi,

Using CC1354P10 and looking at  carrier wave at  both 868.3Mhz and 2.4Ghz and on the 2.4Ghz signal there are several close in spurs beside carrier ( 1.6khz spacing).

The spurs are only present on 2.4Ghz and are present on both +5dbm output and +20dbm PA output which have different baluns in their path.

My pcb is in an idle mode other than the carrier generation and  i do not currently believe spur is generated by onboard pcb noise.

Any ideas what could cause this and why it affects 2.4Ghz output only ?

Thanks,

Ed Currie

  • 0
    TI__Mastermind 18085 points

    Hi Ed,

    A few initial questions for additional context:

    • I get the impression this is a custom PCB, please can you confirm?
    • If this is custom hardware, have you tested this on a TI LaunchPad (the 2.4 GHz, +5 dBm output in particular as there is a CC1354P10 LaunchPad already released)?
    • Is your device configured using SmartRF Studio? If so, what are the PHY settings (in case we need to try and reproduce this on TI hardware)?
    • Please provide measurements at both +5 dBm and +20 dBm (as they are separate outputs).

    There are some measurements you can do to try and narrow down the root cause:

    • Do the spurs vary with the output power setting (i.e. 0 dBm or +14 dBm for example)?
    • Can you try turning off the DC/DC converter and remeasure to see if there is any observed difference?
    • Have you measured/observed any spurs on the VDDS or VDDR power rails?

    Regards,

    Zack

  • 0 in reply to ZC
    Mastermind 6470 points

    In addition:

    - Could you set markers on at least some of the spurs and the fundamental?

    - Could you test with different frequencies in the 2.4 MHz band? What is interesting is if the delta frequency between the fundamental and the spurs change with the fundamental.

    For 868 MHz, have you increased the span and set the RBW = 1 kHz (or lower) to see if you see spurs further out? I would suspect that you have some noise in your system that gets mixed up close to the carrier at 2.4 GHz but are further from the carrier at lower frequencies. Could you disclose what else you have on this board that has some sort or clock or could otherwise generate noise?