BLE antena directionality

[Damien Berger]

Hi, 

I can't found anything in the nrf52840 documentation about the ble antena directionality. I want to use it for indoor location, so i would like to know if it is omnidirectional or not.

When i put the nrf52 vertically, i get variable RSSI results between two boards if i go right, left, front or back.

Would it works better horizontally ?

Any idea on what can i do to obtain an RSSI independent of direction ? 

[Dave_couling]

Antenna directionality is completely dependent on your antenna design.  This isn't really something the Nordic chip is responsible for.  What antenna are you using?   If you speaking specifically about the eval board, it is fairly omni.  RSSI accuracy is always going have a fairly high degree variation even as the devices are stationary.  It what +/-4dB on the nRF51.  So you need to average many RSSI samples to filter out variation.  

RSSI will always be subject to alot of factors: multi-path, interference..etc.

[Damien Berger]

Yes i am using the antena board, i am not connecting any antena.
I use 200 RSSI samples and a filter based on standard deviation to reduce variation.

Results i got are aceptable in three directions (left, right and front when the board is in vertical position), but not with the back direction. I should be able to estimate distance from RSSI but this direction would false the results.

Thank you for your response.