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nRF52 Receiver Senesitivity Enhancement

@nj@ly

Hi,

        We are using nRF52832 for one of our central device. Our peripheral is also based on nRF52. We are facing issues while scanning for the peripheral from the central side. When the central is near to the peripheral, everything works fine. However, as the central moves away from the peripheral after some distance, the central fails to get advertisements from peripheral. We have checked the RSSI value at that distance using nRFConnect App. It is found like RSSI is below -95dBm. Is there any limit set by the SoftDevice  on the receiver sensitivity? If yes, is there any way, we can increase it sothat central can connect with the peripheral from a far distance(RSSI> -95dBm). May I also know what all factors can cause interference in this scenario?

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    Hi,

     

    The Softdevice does not limit on the sensitivity, the nRF52 radio does. If the signal strength incoming is less than the selectivity spec, the signal will physically not be received. The RSSI in the nRFConnect app is the signal strength of the signal in the smartphone, the sensitivity here will probably not be exactly equal to the nRF52, depending on the WiFi/BT chipset.

     

    In order to increase the wireless range you would want to increase the link budget, not necessarily the sensitivity. In the nRF52832 this can be done by adding a front-end-module, which contains both a PA (for TX) and LNA (for RX). The LNA could improve the sensitivity a couple of dB, and the PA increase the output power. When in a connection it will still be limited by the opposing end of the link, if lower TX power and worse sensitivity the signal will get there, but not 'get back' and there will not be an overall range increase. This means that the FEM is needed in both ends. If connected to a smart phone the increase will be limited by the specs of the smartphone.

     

    Another possibility is to trade up for the nRF52840, which supports the 'Coded PHY' feature of Bluetooth 5. With this you can trade in some datarate for improved sensitivity.

     

    Best regards,

    Andreas

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  • 0

    Hi,

     

    The Softdevice does not limit on the sensitivity, the nRF52 radio does. If the signal strength incoming is less than the selectivity spec, the signal will physically not be received. The RSSI in the nRFConnect app is the signal strength of the signal in the smartphone, the sensitivity here will probably not be exactly equal to the nRF52, depending on the WiFi/BT chipset.

     

    In order to increase the wireless range you would want to increase the link budget, not necessarily the sensitivity. In the nRF52832 this can be done by adding a front-end-module, which contains both a PA (for TX) and LNA (for RX). The LNA could improve the sensitivity a couple of dB, and the PA increase the output power. When in a connection it will still be limited by the opposing end of the link, if lower TX power and worse sensitivity the signal will get there, but not 'get back' and there will not be an overall range increase. This means that the FEM is needed in both ends. If connected to a smart phone the increase will be limited by the specs of the smartphone.

     

    Another possibility is to trade up for the nRF52840, which supports the 'Coded PHY' feature of Bluetooth 5. With this you can trade in some datarate for improved sensitivity.

     

    Best regards,

    Andreas

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