Please bear with me, I’m not an RF guy but I’m trying to satisfy my curiosity before I bring up a potential solution for something.
We have done a lot of development of systems that use cellular connections for data retrieval and settings changes. We are looking into doing some changes to the way our system works and testing cellular has always been a bit troublesome because of where we are and our building.
We are looking to update a product to use the SIMCOM 7XXX series modems, it occurred to me having recently gotten into SDR that there may be a more convenient way to test things.
What I want to do is connect the SIMCOM modem to the LimeSDR via cable, this I believe will allow me to use attenuators to simulate various situations, also by using an emulated GSM network, I can test different configurations of network (NAT, dynamic IP, static IP) etc which is something that would be extremely convenient, especially as it will all happen locally without the actual involvement of the internet or a real GSM network.
So, it’s obvious to me that I can use the SIMCOM module with an antenna plugged in, and with 2 antennas plugged into the SDR, one for TX and one for RX. All good so far.
But how do I achieve what I want to do with a physically connected “emulated” link using cable, where one end has one connection and the other has 2! Now, I’m thinking of various solutions, mixers, duplexes etc, but I really don’t know.
Can anybody give me an idea of what I need to achieve this and how I go about it?
I do actually have a colleague who is an RF engineer, but I’d rather have some clue as to what is possible/needed before I make any suggestions.