Help needed regarding GSM module impedance control

[dhanaks]

Hai,

I am designing PCB with SIM900A GSM module. By requirement, the antenna pad of the module must be connected to the (SMA) antenna connector using 50 ohm impedence trace.

The trace length is 784mils and is designed for 50 ohms as per the stack up of the fabricator.

But now for cost reasons, we are wondering if we have to go for a imepedence controlled fabrication or not. There is quiet some cost differences involved.

My question is that since the stack up/impedence are taken care in the layout, is it necessary to go for impedence controlled PCB fabrication or not? Has any one successfully worked with a non impedeance controlled track for SIM900A?

 

[Gunasekaran]

i think impedance is must for all antenna design. using AppCAD software you can calculate the impedance value.

 

[kathiresan]

since you have taken care of the stackup and impendance in the layout i think its fine.

one of my customer also do like this for cost reduction.