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CC1125: Internal Dividers and RF/IF Channels

MattLin
Intellectual 1050 points
Part Number: CC1125

One of my customers is trying to understand the phase noise of the internal synthesizer.  We understand that the phase noise profile for a typical fractional-N synthesizer varies from channel to channel.and assume that is also the case for the CC1125 Fractional synthesizer.  They have a lot of freedom to choose our one fixed channel anywhere in the 137 to 192 MHz range. For best receiver phase noise, what RF channel and IF should they choose when using the CC1125? Or, can you explain the behavior of the CC1125’s internal dividers so that we can perform our own educated search for the best RF channel and IF? For example, for a given VCO frequency, can you explain how to determine the phase detector comparison frequency? Can it be controlled through some of the For test purposes only, use values from SmartRF Studio registers? The goal is to minimize the total close-in phase noise power within ±60kHz of the L.O.

  • 0
    TI__Mastermind 27145 points
    Hi,

    Please ask them to use our SmartRF Studio and select "Generic 169MHz" under Category and select one of the Typical Settings (closer or little higher than their desired Date Rate) then change the RF Parameters as desired and export the Register settings. This is the best way to set the CC1125 to optimum settings.

    Thanks,
    PM
  • 0 in reply to PM
    TI__Mastermind 39860 points
    Since the customer has freedom to choose a fixed channel anywhere in the 137 to 192 MHz range I would recommend using 169.4 - 169.475 MHz. This frequency band is used in Europe for meter reading and we have done extensive characterization of this band. Furthermore, we have a reference design readily available on our web site that supports this band.