Connecting two GSM antennas to a single GSM Module

Hi all,

I want to connect two antennas to a single GSM Module which is on a PCB. One antenna is to be designed on board and cant be moved (will serve as backup) while the other is movable and is connected through a coaxial cable. See attached image for reference.

Both the antennas are to be operational simultaneously and if the external antenna is cut off or disabled, the secondary antenna should continue to operate.

The problem I am facing is in impedance matching. The antennas have an impedance of 50 ohm and the GSM module also has an impedance of 50 ohm. Hence, to connect both the antennas, I need 50 ohm traces. I need to know how to connect both these antennas so that there is no impedance mismatch.

In addition to this, please tell me what will be the effect on the antennas when the same signal would be received by both the antennas. The antennas are connected to the same pin on the GSM Module. Please see the image for details.

Kindly help me out.

Thanks in advance,
Regards,
Salman

How about use some switch? Or some connector that when you insert the antenna, it will auto link to antenna, otherwise it will open or short , so you design a lamda/2 or lamda/4 to convert it.