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CC1101: CC1101 specified band edges and modulated signal bandwidth

Cletus
Prodigy 120 points
Part Number: CC1101

The CC1101 supports several distinct bands as well as several modulation types and data rates. Do the band edges only apply to the carrier frequency, or do they apply to the carrier frequency +/- the bandwidth of the signal.

For example, suppose I had a modulated signal with bandwidth = 200 kHz and a carrier frequency of 779.000244 MHz. This signal would occupy the band from 778.900244 MHz - 779.100244 MHz. The datasheet states that the upper band of the CC1101 is 779-928 MHz, so my hypothetical signal would violate the lower band edge (779 MHz) by 99.756 kHz.

Is this an actual violation, or are the bands edges specified in the CC1101 datasheet only applicable to the carrier frequency (bandwidth doesn't matter)?

Thanks,

Cletus

  • 0
    TI__Mastermind 31610 points

    Hi,

    Band edge requirements are set by regulatory requirements. ETSI, FCC etc.

    The bandwidth of the signal and output power level has to be taken into account when operating very close to the frequency band edge. It is quite common to reduce the output power when working at the band edges.

    CC1101 can operate from 779-928 MHz but the exact settings need to be changed depending on the exact PHY settings. 

    779 - 787 MHz is not used any more for new designs in China so the main operation of CC1101 is typically at 863-870 MHz or at 902-928 MHz.

    Regards,

       Richard

  • 0 in reply to RGW
    Prodigy 120 points

    Richard,

    Thanks for the quick response. 

    I understand that the CC1101's bands are specified based on regulatory requirements, but my question was more hypothetical and in relation to the CC1101's technical capabilities.  Is the behavior of the CC1101 undefined if the carrier frequency is within a valid band, yet the modulated signal's bandwidth overlaps the band edge?

    Thanks,

    Cletus

  • 0 in reply to Cletus
    TI__Mastermind 31610 points

    Hi,

    The CC1101 will still operate even if the bandwidth of the signal is slightly outside the band edge just as long as the nominal setting of the fundamental frequency is within the specified frequency range stated in the datasheet.

    The frequency operation of the VCO and PLL is much greater than specified in the datasheet.

    Regards,

       Richard

  • 0 in reply to RGW
    Prodigy 120 points

    Richard,

    Thanks, that answers my question!

    -Cletus