nrF5340DK Bluetooth PCB Antenna Gain & Transmit Power

[zeuhor]

I didn't find any information about the Gain of the Onboard PCB Antenna of the Developement Kit, nor the effective Transmit power that is available. Where can I find it, and how can I set the desired Transmit Power?

Thanks in Advance

[Vidar Berg]

Hello,

You can change the TX power setting used by the BT controller on the netcore by changing the default CONFIG_BT_CTLR_TX_PWR_0 symbol to one of the other CONFIG_BT_CTRL_PWR_* symbols for your HCI_IPC build. For example, CONFIG_BT_CTLR_TX_PWR_PLUS_3=y if you want to set the RADIO output power to +3dBm. Supported power levels can be found from the TXPOWER register definition.

Instructions on how you can apply configuration changes to child images such as Bluetooth: HCI IPC are given here: Permanent configuration changes to child images.

E.g.,

├── child_image
│   └── hci_ipc.conf

where hci_ipc.conf contains this line: CONFIG_BT_CTLR_TX_PWR_PLUS_3=y if you want to set the RADIO output power to +3dBm.

If you want to verify after building sample that your configuration was applied, you can check the generated .config file in build/hci_ipc/zephyr.

The PCB antenna is supposed to be omnidirectonal so I assume its gain is close to 1, but I don't have a measured value for it. 

Best regards,

Vidar

Edit: antenna gain should be around 0 dBi according to this post:  Rated output and pcb antenna gain of nRF52-DK  and this one: RE: Gain of the PCB antenna of the nRF5340-DK  

[zeuhor]

Thank you very much! After Editing, I found it in the hci_ipc.conf set to the value 3dbm. However, I didn't really notice any difference between the different settings of power, no matter what I set it is around the same value if I look at the nrF connect app from my smartphone. I wonder is it because CONFIG_BT_CTLR_TX_PWR_ANTENNA is set to 0 in my final build? You can see a screenshot of the .config after build:

[Vidar Berg]

The CONFIG_BT_CTLR_TX_PWR_ANTENNA setting should not make any difference when you don't have an external PA/LNA (FEM) on the board. You can try to set the output power to -40 dBm to make it more noticeable. 

[zeuhor]

I see, thanks a lot!