nRF52832 ANT pin Impedance

[Rodrigo Lorenzo Leal]

Hi Nordic Forum!

We're currently tuning our antenna since we runed with some problems during our EMC testing.

In that regard, what is the impedance (both input and output) of the antenna pin (pin 30), when used for Bluetooth?

I know that for the nRF51 series it was 15 + j85 (Between ANT1 and ANT2), but I don't think that holds for the nRF52 series.

Thanks in advance

[bjorn-spockeli]

Hi Rodrigo,

the load impedance of the antenna pin should be 53 + j66 Ohms.

Best regards

Bjørn

[Sugumar]

If the Load impedance of antenna pin should be 53 + j66 Ohms then the ANT pin impedance should be conjugate of the same 53 - j66 Ohms right?

This will help us instead of keeping the load as 53 + j66ohms, we will do matching from pin impedance 53 - j66 Ohms to final antenna impedance with matching circuits.

Please confirm, Because our antenna impedance is not 50Ohms.

[bjorn-spockeli]

Sugumar said:

If the Load impedance of antenna pin should be 53 + j66 Ohms then the ANT pin impedance should be conjugate of the same 53 - j66 Ohms right?

 You are correct! However, you should note that the matching network used in our reference design does impedance transformation to 50ohms AND low pass filtering. So in order to stay with in regulatory limits you will need to add the LP filter component to your custom antenna design. Simply matching the impedance is not enough.