Why MODE=BLE_2MBit can still receive data by MODE=NRF_2MBit

[shchu]

I am a bit confusing about this two mode settings. We plan to use MODE=BLE_2MBit on both TX and RX sides as it can give us about 2dBm sensitivity improvement on the RX side by our measurement.

Something confused us is when RX is set to MODE=BLE_2MBit but TX is NRF_2MBit or vice versa, the RX can still receive correct data from its TX intermittently. However, we noticed that in this (incorrect) setting we feel the RX should be missing data unusually more even though we place the TX and RX closely together.

Is this true for this observation?

As we want to use the BLE_2MBit to take the benefit of more sensitivity improvement, we are testing and evaluating whether it is reliable and mature enough to be used in our end product. Would you please elaborate more for this two modes?

Thank you so much

[ovrebekk]

Hi

The only difference between the BLE_2MBit and the NRF_2MBit modes is the modulation index, ie how far from the carrier frequency the modulated signal will be. 

In BLE_2MBit mode the modulation index is larger, which means the modulated signal is farther away from the unmodulated carrier. This makes the BLE_2MBit mode a bit more resistant to noise, which is the reason why you can see an improvement in sensitivity. 

Since all the other radio parameters are the same it is to be expected that you can some times receive packets when the TX is set to NRF_2Mbit and the RX is set to BLE_2MBit, or vice versa. 

If you are using a proprietary protocol you can choose either of these modes, they are both tested for use in end products. 

Best regards
Torbjørn

[shchu]

Thank you very much for the explanation. I am clear now.