Remote SIM card bank

We are working on a solution with a remote SIM bank.

In the Quectel modem end, we have a Microchip Controller that the Quectel modem sees as the SIM card. This Controller is in 3.3 volt technology. Is it a problem that we connect the 3.3 volt signal to the data-connection for the SIM (normally 3.0 volt), or do we need a voltage level shifter?

I also have a question regarding the baud-rate. We connect the SIM direct to the modem and measures, the clock signal from modem to SIM is 4 MHz, the baud-rate the SIM is using seems to be in the neighborhood of 3000 according to my measurements. Shouldn’t the baud-rate be 9600?

What type of module do you use?


All of our modules currently support 3.3V

We are using this currently: LTE-A EM120R-GL | Quectel

It is the signaling levels from the SIM card I am referring to, normally it would be either 1.8 volt or 3.0 volt, based on response or missing response (ATR) from the SIM card. The signaling level will also be the level for the power supply for the SIM. What we want to do is, responding with ATR to the 3.0 volt supply level, but use 3.3 volt level for signaling.