Why is characteristic impedance of TLs in nRF52840 QIAA Reference Layout v1.0 60 Ohm instead of 50 Ohm?

[donhuanvn96]

According to nRF52840 Product Specification v1.0, all the reference circuits are designed for use with a 50 Ω single-ended antenna. Why is the calculated result by AppCAD 60 Ohm? This  made me disturbed when drawing PCB layout. Can you help me this problem?

[Andreas]

Hi, 

 

There seems to be incorrect dimensions on this trace, yes, this trace should be 50 ohms. It should not be overly critical, the performance hit will not be immense but for your own design you would want to adjust the gap and width dimensions to get as close to 50 ohms as possible.

 

Best regards,

Andreas