NRF52832 WLCSP ANT pin impedance

[madroche]

Hello!

I am wondering what the impedance looking into ANT pin 30 is for the NRF52832 WLCSP package. Does the recommended 1pF shunt and 3.3nH series transform the pin impedance to 50 ohms? I am trying to simulate an antenna match and need more information to do so. Please let me know any details about how to proceed. Thank you. 

Madeleine

[Kaja]

Hi Madeleine,

Does the recommended 1pF shunt and 3.3nH series transform the pin impedance to 50 ohms?

 - Yes they do. 

You can always simulate, but the components values needs to be tuned on the on the actual PCB. For the matching network for the radio this tuning is based on the actual RF emissions, not the impedance, to control the harmonics and output power. When you do this, you indirectly get the right impedance. 

For matching the antenna, you should put in a matching network, like a Pi or T, and the transmission line between the matching networks should be 50 Ohm. - Here you tune based on the impedance. 


Best regards,
Kaja

[madroche]

Ok thank you! Do you know the S11 impedance of the pin itself? Without the recommended LC filter? Please let me know, thank you. 

[Kaja]

Hi again, 

I don't know the exact impedance, but it's around 80 Ohm. --> The matching components transforms it to 50 Ohm. 

Best regards,
Kaja

[madroche]

Working backwards from the L network (3.3nH series and 1pF shunt to the the source) I am seeing the impedance as 80 - j44 ohms. Can you confirm this value is accurate with someone? Thank you 

[Kaja]

Hi, 

we have not measured the exact impedance, but as I said it should around 80 Ohm, and that is what you are seeing. 
This is the impedance you should be seeing when both the radio and antenna is matched to 50 Ohm. 

Best regards,
Kaja