Effect of PCB vias on GSM signals

Hi,

I am trying to find if it is ok to put vias in the path of GSM signals? I know that vias should be avoided on high speed traces but is there any design note describing the effects of vias on GSM signals? What number of vias are permissible? Do they change the impedance of the trace?

I am using a PCB antenna which will be mounted on a larger PCB and a track will run through the antenna to the GSM module.


Thanks in advance,
Regards,
Salman

ANS: Avoid if possible, if not put as many as possible to guard the signal
ANS: Put as many as possible to guard the signal
Ans: Yes, do take care/control by having taper in the 50 ohm transmission line