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CC1110 Unexpected sub carrier found at 5Ghz band when TX

Jay Kim
Intellectual 475 points

Hello,

We made our own board with CC1110 and this board runs good at frequency range 917~923Mhz so far.

But recently we found there's unexpected sub carrier frequency at 5~6Ghz band been also generated when TX.

I like to know which can possibly cause this how to eliminate these 5~6Ghz sub carriers.

Thanks in advance!

Jay

It's also generated when using SmartRF Studio and here's what I do.

(1) Open SmartRF Studio7, choose CC1110

(2) Choose Typical setting "Data Rate : 38.4 kBaud, Dev : 20kHz, Mod : GFSK, RX BW : 100kHz, Optimised for sensitivity"

(3) Change Base frequency as 919.1Mhz

(4) Run continuous TX

  • 0
    TI__Mastermind 39860 points

    The spurs are the 6th and 7th harmonics of the fundamental. 

    I assume you are targeting compliance with FCC 15.247 or 15.249.

    15.247: Requirement for 6th harmonic is -41.2 dBm. Requirement for 7th harmonic is -20 dBc.  The antenna has a finite BW and will probably attenuate the 6th harmonic well below the limit when you do radiated measurements. 7th harmonic is not a problem.

    15.249: Maximum output power is -1.23 dBm. Requirement for 6th and 7th harmonic is -41.2 dBm. The antenna has a finite BW and will probably attenuate the 6th and 7th harmonics well below the limit when you do radiated measurements. Note also the limitation on max output power.

  • 0 in reply to Sverre
    Intellectual 475 points
    Hello,

    Thanks a lot for your information!