RE: nRF24LE1 antenna 50 ohms impedance matching questions

Kevin — Thu, 30 Aug 2018 07:00:17 GMT

Hi Andreas,

Thank you so much for your detailed explanation and guidance!

i have send you my design files to you, please kindly help to review and give advice if any, thank you !

Best Regards,

Kevin.

RE: nRF24LE1 antenna 50 ohms impedance matching questions

Andreas — Tue, 28 Aug 2018 11:55:32 GMT

Hi,

Maybe, maybe not. Based on my own experience with this I would not count on it. Note though that even if it is not perfectly 50 ohm, you will still be able to achieve wireless communication, just at a smaller range than if it was tuned. You might want to add an unpopulated pi network in case tuning is needed in the future (series component can be 0ohm resistor)
The components do differential to single ended matching, and low-pass filtering of harmonics and spurious. If the reference layout is not replicated, performance will differ. You might still get decent output power, but see a drastic increase in harmonics.
The balun component in screen 2 replaces the lumped matching network in screen 1, yes. It should not be as dependent on the thickness, but as you have no components to adjust the value of, it is paramount that you replicate the mounting(layout) with regards to the nRF and grounding exactly. Feel free to submit your design here for a free review.
With the balun, the importance of the 50 ohm transmission line becomes larger. In your current design the transmission line between the antenna and C6 is so short that it will not cause any mismatch. With the length between the antenna and a hypothetical balun, it will be long enough that you would want to dimension the transmission line to 50 ohms to avoid risk of any performance hit. It's not the end of the world if it is 52 ohms or 45 ohms, but closer is of course better. Impedance control should not be needed, just use a free transmission line calculator, e.g. AppCAD.

Best regards,

Andreas