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Original question:

CC1125: Listen Before Talk (LBT)

CC1125: Carrier Sense Threshold

Andy Neil
Guru 35595 points
Part Number: CC1125


From the CC1125 User Guide:

And:

What is the actual usable range of the threshold?

presumably, it doesn't actually go right down to -128 dBm or up to +127 dBm ?

  • 0
    TI__Mastermind 27145 points

    Hi,

    We will look into it and get back to you ASAP. Please bear with us.

    Thanks,

    PM

  • 0
    TI__Guru**** 317180 points

    I believe that you can set the threshold in this range but normally you want to set this around the sensitivity limit. This is typically something you need to do some testing at the location you want to deploy your product. This is because the noise floor could be fairly high at some locations. If the sensitivity is -100 dBm and the noisefloor is at -80 dBm you have to set the threshold a bit higher than the noisefloor to avoid false triggers.

    What is your intended use of carrier sense? If it's related to the LBT question you need to set the threshold to the ETSI limit.

  • 0 in reply to TER
    Guru 35595 points

    Yes - the question was what is the actual, meaningful, usable range - as the 8-bit signed numerical range of  -128..+127 dBm exceeds (in most cases) the receiver specs.

    Of course, it will depend on the deployment environment. But was wondering if there were are other internal limitations.

    TER said:
    If it's related to the LBT question you need to set the threshold to the ETSI limit

    It is. So the motivation for the question was, can it achieve those limits?

    (I would assume it must - as it's specified to be compliant - so just confirming)

    EDIT

    Another way to put it:

    I guess the receiver sensitivity puts a minimum "floor" to the threshold - but is there any further limit/recommendation; eg, that it should  be at least X dB above the sensitivity "floor" ?

  • 0 in reply to Andy Neil
    TI__Guru**** 317180 points

    The register is 8 bit and it's not any limitations on what you set this register to since you can't do anything damaging. If you set the register to "not logical" settings you will either don't have any carrier sense threshold (no gating) or if you set it too high you will always be gated. 

    Typically you want to set the threshold slightly above the sensitivity limit to not be trigged by noise but if you set it too high the sensitivity will be limited.