NRF21540 RF port matched to 50ohms

[rolandash]

Hi,

I am considering a NRF52833 + nrf21540 combination. I see in nrf21540 product specification mentioned that 

• Single-ended 50 Ω matched input and output

So does that mean:

for the 21540 output RF port to antenna, I do not need matching network for 21540 any more, only antenna matching components is needed? What is the purpose of L1/C2 in the 21540 PS sheet Fig.13 ref-circuit then?

I do not find if 52833 RF port is also 50ohm matched in 833's specification. Is 833 RF output is also 50ohm matched?

Thank you.

[JONATHAN LL]

Hi, 

The nrf52833 and other nrf52 series chips needs matching components to be 50 Ohms, but also to filter harmonics as this is a equally importen factor. 


Here is a example of how it is normally done, if you where to include the nrf21540(including the components form the reference circuitry) then that would be after the C3 and L1 component in the picture above. 

It is still recommended to include the series inductor and shunt capacitor for the ANT ports.

If you have a specific inquiry then i do recommend that you make a new ticket and ask for a HW review and information on specifics of you design. 

Regards,
Jonathan

[rolandash]

Jonathan LL

thank you. I will do that.

One thing i would like to make sure before i finished up the schematic is if the L1/C2 in 21540 ref-circuit used for matching 21540 or matching antenna? It looks like it is intended to matching 21540, as there is another shunt capacitor C3 can be used to tunning the antenna. But since 21540 is already 50ohm matched so i am bit confused, should C3 alone is enough here?

[JONATHAN LL]

rolandash said:

One thing i would like to make sure before i finished up the schematic is if the L1/C2 in 21540 ref-circuit used for matching 21540 or matching antenna?

 The components are both for 50ohm matching (fundamental frequency) and filtering (harmonic frequencies)

Regards,
Jonathan