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CC2640R2F: BT5 LRM Practical sensitivity in the range tool

Albin Zhang
Expert 6060 points
Part Number: CC2640R2F

Hi, I tried to calculate the LRM range with the tool. and found the practical sensitivity is only -87dBm. I put every factors to the normal one but the link margin. 

could you comment why it reserves 16dB if there is no antenna diversity? is it for real? If use 16dB, the range 389m, it is far behind of 1.5km 

BR. Albin

  • 0
    TI__Guru**** 317180 points
    Richard is on vacation so I'm not able to double check with him why the link margin is set this high but I assume it's related to how sensitive BLE/ 2.4 GHz is for a variety of effects. This is not a number with absolute accuracy, it's more to have an indication of how many dB you have to be above the noise floor to be ensured a connection regardless of the exact placement of the DUT.

    I see that you have used 10 m above ground for both RX and TX, is this a valid use case?

    The tool is meant to give an indication of the range possible to obtain given a set-up. The real range could be both loger or sharter in the real words since it's not possible to include all factors in an excel sheet.
  • 0 in reply to TER
    TI__Expert 6060 points
    Hi Torestein,

    10m hight is not real case, i just want to ignor the "hight" factor impacts to the estimation results.

    Understood it is just an estimation tool.
    I am just wondering the theory of the "16dB" reference

    BR. Albin
  • 0 in reply to Albin Zhang
    TI__Guru**** 317180 points
    Could you ping me next week and I'll check with Richard where 16 dB comes from.
  • 0 in reply to Albin Zhang
    TI__Mastermind 33100 points

    Hi Albin,

    With multi-path propagation, the received signal strength can vary up to 10 dB within a square meter. In order to guarantee that the radio quality is not effected by placement in a square meter at least 10 dB needs to be added to the link margin. 

    In the range calculation, the "Mean Effective Gain (MEG)" of the antennas is used instead of "Gain" since this is more useful for devices that are not in a fixed position. For a perfect dipole the "Gain" is typically 2.1 dB but when using "MEG" then this value is 0 dB. 

    So when using perfect dipole antennas with MEG parameter , the link margin of "16 dB" is only "11.8 dB" with traditional gain values of the dipole antenna. For comparisons of earlier versions of the excel tool.

    The level of the link margin can always be discussed and there will never be one answer since this will vary from customer to customer. 

    Hope this helps where the 16 dB has come from.

    Thanks, Richard

  • 0 in reply to RGW
    TI__Expert 6060 points
    Richard,
    thanks. it's clear.
    BR. Albin