Feed line for connecting SMA connector on PCB

[mrinalmani]

Hi!
Please tell me how to connect the RF output pin of 800MHz RF IC to a SMA connector.
Can I simply route the wires from the IC to the connector just like any other components or do I need to take some special care since this is a RF circuit.
Does the length of connecting PCB trace have an impact on the performance?

Thank you

 

[PlanarMetamaterials]

Can I simply route the wires from the IC to the connector just like any other components or do I need to take some special care since this is a RF circuit.

Yes, you need to take special care. The characteristic impedance of the line should be matched to the output impedance of the IC, and the impedance of the SMA connector.

Does the length of connecting PCB trace have an impact on the performance?

Not if the line is properly impedance matched.

 

[mrinalmani]

Thanks for the reply!
I am interfacing SIM-5360 module. I need to connect the antenna pin to SMA connector. The SMA connector is 50 ohms (datasheet).
I am attaching a simple circuit.


There is a tuning circuit between the antenna and the module pin. I have simply copied this tuning circuit from a development board. I know nothing about this. Is this OK?
Any suggestions for length and width of PCB trace connecting the module pin to the antenna?

 

[PlanarMetamaterials]

It's a bit hard to say with only the circuit model, but so long as the line is fairly short I think that should be OK.

 

[mrinalmani]

Thanks for the reply.
I'll make the trace around 10mm in length.
Also, is the tuning circuit ok?

 

[PlanarMetamaterials]

10mm should be fine at 800 MHz.

I'd have to know about the output of the IC to comment on the tuning circuit, but it seems reasonable to me.

 

[FvM]

SIM-5360 has 50 ohms matched antenna output and doesn't need a matching circuit when connecting to a SMA jack. R48 in the schematic is a zero ohm jumper by default and the capacitors are unpopulated. If an impedance matching is required in special cases, "R48" would be an inductor rather than a resistor. It's also unlikely to achieve wide band matching for quad band with a single LC pi-filter.

The trace should be dimensioned near 50 ohm, either as micro strip or coplanar waveguide with ground.