Antenne requirements nRF52840 - Antenna tuning

[bubble23]

Hi,

I have a question about the whitepaper nwp-017.pdf. It is described under the chapter "Equipment needed to tune an antenna" that you have to attach a coax cable where you want to measure the impedance. So to tune the antenna I have to measure behind the matching network? Or can I measure in front of the matching network with the embedding and de-embedding method (including the matching-Network)?

What is the impedance at the output of the nrF52840 chip? We need the information for research and test.

thanks in advance

[JONATHAN LL]

Hi,

What is the impedance at the output of the nrF52840 chip?

The RF impedance is 50 Ohm, se ref pic from nrf52840 CKAA schematic.



For tuning of the antenna the coaxial cable is attached before the matching network, se picture. 

The wording may change depending on what perspective you have, if you are looking form the antenna side or from the radio side. Hope the illustrations above clarifies.

 Regards,
Jonathan

[arif.ozcan]

Hi,

Could you suggest me fine-tipped coax probe like that figure ?

Thanks

[JONATHAN LL]

This is the product we use; EZ-47/M17 , but I believe that you can use any thin copper jacked coax cable with a thin diameter.  
Regards,
Jonathan