How to control the RF impedance?

[realealon]

Hi

I got some questions about the RF part of the ref schematic. 1, why the bias voltage for ANT1 anf ANT2 are not the same since they are differential lines? 2, what's the impedance from L1 to ANT1 and ANT2? Is it 15+85j? How am i gonna tell the PCB manufacturer to control the impedance?

BR ealon

[FormerMember]

In order to get the right impedance the reference schematic/layout should be followed. The matching network in the reference layout matches the chip to 50 Ohm.

[realealon]

Kristin

Yet the impedance seen from the ANT1 and ANT2 to the matching network is 15+85J in the NRF51822 datasheet.

[realealon]

And the ref schematic/layout doest not specify the matching impedance.

[Marc Nicholas]

The reference schematic does not have a matching network. You will need a Pi matching network that's appropriately tuned for your design.

I believe that Nordic still offer a free antenna tuning service, but you should speak to your sales rep about it.

-m

[FormerMember]

Which chip do you use?

There are two matching networks that are needed, one for matching the chip to 50 Ohm, and another for matching the antenna to 50 Ohm.

The reference design for a specific chip contains the matching network for matching the chip to 50 Ohm. In addition, a matching network (a shunt component or a pi-network) is needed for tuning of the antenna, see the Antenna tuning white paper chapter 4.

Yes, we help out with antenna tuning. For request regarding antenna tuning, please open a case in Nordic support system.