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CC1200: configured LO divider to 8 . Spectrum Analyzer shows activity in 868 MHz

Bart Jooris
Prodigy 70 points
Part Number: CC1200
Other Parts Discussed in Thread: CC1120EMK-420-470

Dear,

on a Zolertia Remote rev.b. 

we configured the register settings from smartRF studio (second listed in the 433MHz configurations)

// Carrier Frequency = 433.999939 
// Deviation = 3.986359
...

// Symbol rate = 1.2 

We connected the RF-output via coax (and 20dB attenuator)  directly to our MDO4051B (see screenshot, no signal can be noticed during reset of the Zolertia)

and we noticed that our Zolertia is active in the two bands so both 433MHz and 868MHz!

Which is not the case with pure 868MHz config from SmartRF studio.

Can you help us to figure out what went wrong?

Thanks a lot,


Bart

  • 0
    TI__Mastermind 27145 points

    Hi,

    It looks like you are seeing the 2nd Harmonic of 433.99MHz ( 434*2 = 868MHz).

    If you want to use at 433MHz, you need to use 433MHz band board or modify 868MHz band board with 433MHz design.

    Balun and Filter are different from 868MHz design to the 433MHz design.

    Thanks,

    PM

  • 0 in reply to PM
    Prodigy 70 points
    Hi,

    thanks a lot for your quick reply!
    Based on your info we are now into SWRR122...
    but we will first buy some CC1120EMK-420-470 :-)

    Kind regards,

    Bart