Do PCB Vias affect Antenna performance?

[Sherry1]

I am using a GSM (900/1800MHZ) and 1.5GHz external antennas connecting to the GSM module.
- The U.FL connector is on the bottom of PCB
- The Module is on top of PCB
- And the feed trace on top layer will use a Through hole via in PCB to go to bottom later and connect to U.FL (surface mount connector)

My question is , How much an Inductance of a via is significant at these frequencies. Will I need to revise my impedance matching network ?

Note: My PCB is small in size(5cmx 5cm)

 

[FvM]

You can consider a via as short transmission line segment and you'll be always able to adjust the via dimensions between capacitive (Z < 50 ohm) and inductive (Z > 50 ohm) behaviour. The adjustment involves modifying via and antipad diameters and possibly placing multiple vias in parallel.

The small mismatch of a short via can be usually neglected compared to expectable antenna VSWR. But as you have an antenna connector, it makes sense to use as reference point for fine adjustment of the output impedance - with or without vias