Optimum rf impedance to present to transceiver output.

[DashRiprock]

I am tying to match the nRF52840 rf output to my 50 ohm 2.45GHz pcb antenna.  What is the optimum rf impedance for best transmitter/receiver performance?  The markings on the chip are N52840 QIAAC0 1908GK. 

Thankyou,

Doug

[Martin Sivertsen]

Hi Doug,

As mentioned we provide the service of tuning the radio- and antenna matching networks in-house, if you want to you can send two PCB's to us and we can do it for you.

We also have a white paper on antenna tuning using a VNA. 

It's not just about adjusting the the output from the radio to the right impedance though, it's also about subduing 2nd, 3rd and 4th harmonics so the product passes certification, we use a spectrum analyzer to make sure we get the harmonics sufficiently low.

For example: C26 (in your case) with a value of 0.8 pF together with the trace that goes through VSS_PA creates a notch filter effect that ideally helps subdues 2nd and 3rd harmonics if the reference layout for the PCB is followed exactly.

DashRiprock said:

The problem is how will I ever know if I have this right without doing radiated measurements?

You can get it as close as you can by doing conducted measurements and adjusting the matching network components accordingly.

Let me know how I can be of further assistance.

Best regards,

Martin S.