nRF21540 matching components with nRF5340

[rikhard]

Dear Nordic,

We are developing nRF21540 + nRF5340 solution.

As there seems to be many versions of matching components depending on which source of information is used, could you simply describe which matching components are preferred

• In between of nRF5340 (CLAA) and nRF21540?
• At antenna port of nRF21540 assuming that nRF5340 is driving the front-end?

Best regards,

rikhard

[Jared]

Hi,

There is mainly 3 matching networks, the first is the matching network for the radio on the nRF5340, which consists of a Pi network. Here you should follow what is recommended in the nRF5340 reference design. See the outlined components:

RF output from the matching network from the radio should be connected to the input series capacitor to the FEM:

The components marked in red should be followed as is. The components in the blue square are for matching the antenna. Here you should follow what is recommended in the datasheet of the antenna. For example in the datasheet of the 2450A T18B100 antenna, it recommends a T-network. 

I hope that answers your questions.

regards

Jared 

[rikhard]

Thanks for good details. One more question: does nRF5340 has internal DC block? We might have to add a filter in between nRF and xFEM and that would require shunt inductor(s) before the DC blocking capacitor.

[Jared]

What kind of filter and for what purpose? Additional filters is usually not needed as the matching network for the radio( L1+ C1+ L2 +C19) filters out harmonics.  

best regards

Jared

[rikhard]

To make sure that powerful out of band spurious signals / jammers will not be an problem to receiver. The very selective BAW needs to have shunt inductors placed in input and output.

[Jared]

Hi,

I see, the nRF5340 does not have an internal DC block, the ANT pin is DC-grounded.

regards

Jared