I am working on a project that uses small Bluetooth low energy (BLE) beacons to track important items. However, we have run into a situation where one location will store these items underground in a metal storage container, causing the system to be unable to "see" the beacons inside, and thus thinking they have been lost, stolen, etc.

The idea to fix this is to design a BLE repeater, that sits inside the underground container and picks up the beacons' advertisement packets and then re-advertises them outside the container where the main system can see the signals. (The beacons only advertise once every 10 seconds, so data bandwidth is not an issue.)

The problem is that we would need an antenna inside the container to pick up the advertisements from the beacons, but also an antenna outside the container to retransmit the data. I'm no RF expert, and just beginning to dip my toes in the BLE world, but is there a way to connect two antennas in such a way to a single BLE module that could either listen/broadcast on both antennas or multiplex between the two?

Or would the best solution be to have two BLE modules, one responsible for scanning for beacons and the other one responsible for retransmitting the advertisements, with a communication link between them on a PCB?

Thank you for any input you can give!

  • \$\begingroup\$ Two BLE modules might be the most straightforward solution if you want to optimize the amount of engineering time. \$\endgroup\$
    – EarthLord
    May 20 '20 at 9:33

I managed to find a couple of RF experts at my company and they recommended looking into 3 options:

-A two-way power divider to connect two antennas simultaneously

-A SPDT RF switch which takes a couple logic inputs and selects between two RF output paths

-An RF circulator which only allows signals to pass one direction in and out the 3 ports.

After looking at each solution I've decided to try a prototype with a surface mount SPDT switch since they can be found for a few dollars and fit on a small PCB.


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