Impedance matching (RF)

[ECE1088]

I have deigned a pcb which includes an SMA connector and 3g module. I'm a novice in RF field. The RF trace width that i Have calculated for 50 ohm impedance is 0.427mm.(core thickness=0.27mm and pp=0.076mm). I need to get my gerber verified before sending it to manufacturer. I've attached my gerber file.

Please help.

 

[asimlink]

Hi,
To correctly tell pcb trace width for specific characteristic impedance (50 ohms in your case), you need to explain.

1. PCB trace width
2. PCB trace height above GND Plane
3. PCB material (FR4 or anyother) so that one may know thr Er constant for the mateial
4. Trace geometry / Configuraion (example : microstrip configuration or stripline configuration)

You have a microstrip configuration as you only have top and bottom layers in your pcb. I see in your gerbers that you dont have any copper plane under your RF signal which is originating from SMA Connector. To have controlled characteristic impedance you should have Gnd plane under the trace. In your case the GND place could be drawn in your bottom layer.

I would suggest you to use free tool from Satrun PCB Design Inc. :

1. Saturn PCB Toolkit: https://www.saturnpcb.com/pcb_toolkit.htm

You can use this tool to calculate trace width required for any given characteristic impedance and for any configuration (microstrip or stripline)
It is a very easy tool that you will learn in few minutes.

Regards,

Asim

 

[Ow@i$]

You should include a ground plane at the bottom it is some what you can say necessary for RF