https://devzone.nordicsemi.com/f/nordic-q-a/47278/transmission-line-impedance-on-nrf52840-pca10056-development-boardHi, I am trying to design the transmission lines based on the reference board design from Nordic. I opened up the Altium layout file for the board which I downloaded from the website. I measured the RF trace width to be around 30 mils, and gap betweenen-USTelligent Community 13Wed, 15 May 2019 06:19:08 GMThttps://devzone.nordicsemi.com/thread/187121?ContentTypeID=1Wed, 15 May 2019 06:19:08 GMT137ad170-7792-4731-bb38-c0d22fbe4515:804cae44-c568-4e69-b103-33c02f0be858Kaja<p>Hi DebbyX,&nbsp;<br /><br />so the impedance looking directly into the radio is not 50 Ohm, this is why we use a matching network at the output, to transform the impedance to 50 Ohm (and also filter away harmonics). We do the same with the antenna, use for example a pi-network to match the impedance to 50 Ohm. The transmission line should be 50 Ohm after the matching network for the radio. from the radio to the matching network, you can just use the trace from the reference design.&nbsp;<br /><br />I have this picture of the impedance, that I made for the nRF52832 (so the matching network is different), but it illustrates the impedance you see when both the radio and antenna are match to 50 Ohm.&nbsp;<br /><img alt=" " src="https://devzone.nordicsemi.com/resized-image/__size/640x480/__key/support-attachments/beef5d1b77644c448dabff31668f3a47-c7cea699104c40ed84e939520339608a/impedanceGen.png" /><br /><br />Best regards,<br />Kaja</p><div style="clear:both;"></div>