Multiplexing ST25R3911B's antennas in single ended configuration

[Zahra]

Hello all,

I'm currently working on a project to detect multiple objects on a grid. I plan to put NFC tags on each object and use only one reader to detect all of them. One of the solution is to have one reader's antenna per cells.

Is it possible for me to use multiplexers at the output of the matching circuit in single ended version of the ST25R3911B reader? Will the ST25R3911B reader be able to detect the signal coming from multiple antennas?

Thanks and best regards

Azzam Zahra

[Travis Palmer]

Hello Azzam Zahra,

You can use a multiplexer to switch from one antenna to another. The tricky part is to find an IC which fits to the requirements.

Main criteria are, that the on-resistance should be below ~5Ohm. Also the voltage limit of the multiplexer should be according. A typical value of antenna voltage can be 40Vpp. If the Q-factor is maximized, it can easily go up to 80Vpp.

You can also try to build up a multiplexing circuit consisting of transistors.

BR Travis

[smithderek2000 · Accepted solution]

I've spent quite awhile on this problem. Ended up using relays but customer didn't like the clicky-clack. Now designing in the TI TMUX6221 / TMUX7221; it's an analog switch that I've tested with the ST25R3911B and it works.

The problem with the RF switch ICs is that they're not really designed to operate at 13.56MHz; most start at 100MHz+.