nRF52840 ANT output impedance matching method

[Hiep Le]

Hello everyone,

I am designing a custom board based on nRF52840-QIAA, so my question is:

The output radio impedance of the nrf52840 is not 50 ohm and now I want to calculate and select the components myself to match 50 ohm, so what tools and methods should I use? Can I use the VNA to do this?

[ketiljo]

You need to make sure that the impedance transformation is correct and that the low pass filtering of the harmonics are sufficient. The by far easiest is to use the reference design, btu if you deside to spend some time on this, you need to measure the output power and the harmonics in addition to S11, seen into the matching network from the antenna side with the radio in TX mode. Aim for ~60 to 70 ohm here. 

[Hiep Le]

Hi ketiljo,

Thanks for your support.

If I want to use the antenna tuning service from Nordic, what I need to do? Do I need to send my hardware to Nordic company? and how is the process for this service?

Best regards

Hiep Le

[ketiljo]

Yes, you need to send it to Nordic. You need to follow the reference design, no exceptions. Open a new private case and post the design there, schematic and gerber files.