nRF52840 matching network for pin 31(ANT), matching circuit needed for regulatory requirements, EMC

[bjornshnrf]

Hi,

We are close to going into a certification process but before we start we need to be sure we are not missing out on your recommendations with regards to EMC performance.

Is the radio matcing network needed for other purposes than matching towards 50ohm? Is it needed for regulatory approval? 

Can you share the impedance at pin 31 (ant port) of the nRF52840?

Thanks,

Regards

Bjørn

[Kaja]

Hi Bjørn,

yes a matching network for the radio is needed to be able to pass certification. 

The point of the matching network is to filter the harmonics and to optimize the output power. 

The impedance measuring directly on the ANT pin is not possible to do, as you will load the radio with a 50 Ohm load, and this is not the load you want on the radio. 
The impedance will also change depending on the radio setting. 

I will add the impedance measurements of the matching network, as this the load the radio sees when it has the correct load.

Four components matching network: 5127.nRF52833 QIAA matching network.pdf

Three components matching network: 0830.nRf52840 QIAA matching network (1).pdf

Both matching network are valid for nRF52840 QIAA, but if you plan to use 8 dBm as TX power I will recommend the matching network with four components as this filters the harmonics best. 



Have you gotten a HW review from us? If not, upload the HW files to the case, and I can have a look.

Best regards,
Kaja