https://devzone.nordicsemi.com/f/nordic-q-a/5557/antenna-with-long-run-using-balun-where-should-balun-be-placedWe&#39;re designing a board with the nrf51822 QFA part. Due to design constraints, the chip will have to be about 15mm from where the antenna port will be. The routing to the antenna port will have a decent keepout and no planes directly underneath. It willen-USTelligent Community 13Fri, 13 Feb 2015 10:06:50 GMThttps://devzone.nordicsemi.com/thread/19461?ContentTypeID=1Fri, 13 Feb 2015 10:06:50 GMT137ad170-7792-4731-bb38-c0d22fbe4515:e9be3635-f399-4612-9c07-a1549794f4adAsbj&#248;rn<p>You should go for option 2and keep the differential tracks as short as possible and the balun as close to the chip as possible. Then from the 50 Ohm output you do a 50 Ohm trace to where you need it. <a href="http://www.hp.woodshot.com/">We use AppCAD to calculate the dimensions on the 50 Ohm trace.</a></p> <p>The problem with running the differential lines is that every millimeter of trace at 2.4 GHz on FR4 will be just about 1 nH of inductance and also introduce stray capacitance into the system. When the inductors used are in the low nH range themselves, the additional trace inductance become a big problem. So keep the balun as close to the chip as possible and the differential routing as short as possible.</p><div style="clear:both;"></div>