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

[Steve]

Hello,

I have the same question as noe in the follow up.  Is the optimum load impedance of the antenna pin dependent on package for the nRF52832?

Thanks,

Steve

[bjorn-spockeli]

Yes, the WLCSP package does not have the series inductance from the bonding wire used on the QFN. 

[Sugumar]

What is the ANT pin impedance for QFN package? Since we are using QFN package not WLCSP.

We will incorporate a LPF for harmonics suppression with detailed EM simulation by using our layout.

But we can't follow your eval-board layout and components, Because we are using custom PCB antenna with non 50 Ohm impedance.

So we will match your antenna pin impedance to our antenna impedance using LC but with our impedance values.

To do the same we need the ANT pin impedance or Recommended Load impedance value for QFN Package?

[bjorn-spockeli]

The ANT pin impedance for the nRF52832 QFN is 53 + j66 Ohms.

[Sugumar]

Whether ANT pin impedance for the nRF52832 QFN is 53 + j66 Ohms or Load Impedance?

If Pin impedance is 53 + j66 Ohms is then my load impedance should be 53 - j66 Ohms.

Please confirm.

[Steve]

So what is the pin impedance and recommended load impedance for the WLCSP?  I don't typically assume a conjugate match is ideal unless the manufacturer recommends it, since load impedance can impact power, stability, harmonics, etc, and sometimes the optimal load isn't the conjugate due to these other factors...

[Sugumar]

I didn't understand, if I am not following manufacturer recommended dielectric material (FR4) and matching components and Antennas

Then how should I match the antenna port and get best performance for my custom design?

What is the typical steps should I use it to achieve? I know conjugate can be used to do proper impedance matching and even though with the matching LC values able to suppress the harmonics if proper EM simulation is done.

bjorn-spockeli  Please suggest how to proceed.

[ketiljo]

Measure into the matching network with the chip in TX mode and adjust the values of the matching network , C and L, until you see 50 ohm. You must check the levels of the harmonics as well with a spectrum analyzer.