I'm designing a PCB including Quectel's BG77 LTE module. In the application note I read:
The antenna ports have an impedance of 50 Ω.
Then this reference design is proposed for the antenna interface:
It is recommended to reserve a π-type matching circuit for better RF performance, and the π-type matching components (R1/C1/C2) should be placed as close to the antenna as possible. The capacitors are not mounted by default.
I can't understand the aim of this network when the antenna's impedance (50 Ω) is the same of the module's input port and the transmission line that connects the antenna to the module is designed to have the same impedance.