nRF5840 Impedance matching and filter

[JesB]

Can you share the source impedance measurement for the nRF52840-CKAA? Is the T-network only for impedance matching? Do i need a filter for harmonics if I'm planning to transmit at max power?

[JONATHAN LL]

The network serves both purposes, matching to 50 Ohm and filtering of harmonics. If you follow the follow the reference layout and schematic\component values then it should preform OK without any additional filtering. 

But all designs usually differ to some extent so we recommend that all devices are tuned to achieve best results. Only additional components that you would need that we recommend is to include a matching network for the antenna. So a extra T or Pi network or whatever the antenna manufacturer recommend if you are to go for a of the shelf antenna.

You can follow the info on schematic here :https://infocenter.nordicsemi.com/topic/ps_nrf52840/ref_circuitry.html?cp=4_0_0_6_2_8#concept_k2r_5q2_2cb, and download the HW files for reference here:  https://www.nordicsemi.com/Products/nRF52840/Compatible-downloads?lang=en#infotabs

We do design review so you can ask for a review and we will provide feedback on schematic and layout.


Regards,
Jonathan