Hi,
I am designing a custom board based on nRF52820 SoC. I see that its matching network is different in reference compared to previous SoCs on which I have worked i.e. nRF52810, nRF52832 & nRF52840. I want to know if I use reference design of nRF52820 then can I use the same monopole antenna of nRF52 DK with this matching network?
Or I also need to replace matching network with that of nRF52 DK for using this monopole anternna?
Thanks
Shahid
Hi, Shahid.
The matching network found in the nRF52820's reference schematic (reference matching network on nRF52820-QDAA shown below) is there to optimize the output power and suppress the harmonics from the radio.
Thus, this is sort of independent from the antenna's matching network which is there to tune the antenna closer to the 50 ohms of the coplanar waveguide it is connected to.
When looking at the nRF52 DK, with hardware files found here, the matching network circled with orange is the matching network of the nRF52832's radio, equivalent to the nRF52820's matching network shown above. The single shunt component circled with violet, is the matching network of the antenna. For monopole PCB antennas it is usually sufficient with a shunt component, as they can also be tuned by adjusting their length. As a consequence, it is in most cases a good idea to add some extra length for tuning purposes because the characteristics of your PCB are likely to differ from the ones of the DK's PCB.
So, in short, you should use the nRF52820's radio-matching network, in addition to the antenna's shunt component. The antenna should also have some extra length compared to the antenna found on the DK to facilitate the tuning of it.
Best regards,
Mathias
