PCB Antenna Width

I am looking over the stack-up for the dev board which I received from an FAE and has designed in a 50mil width PCB antenna. I am using this online calculator here:

emclab.mst.edu/.../index.html

From this calculator and based on the board specs I am not seeing 50mil being a 50-Ohm trace with the given PCB stack-up. Can you explain why/how Nordic arrived at 50 mil with the attached stack-up? I am not sure why my calculations aren't matching Nordic's.

4layerstackup.PNG

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  • Perhaps another way for you to look at the antenna is as an impedance matching device. Assume that the output impedance of the radio is 50ohm (this can really be any value), and that the input impedance to free space (air / atmosphere / whatever you want to call it) is about 377ohm (see en.wikipedia.org/.../Impedance_of_free_space). It's a matching device, and should not be considered a stripline. Discussions about the length of the antenna, "shape" of the antenna, etc are for another day.

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  • Perhaps another way for you to look at the antenna is as an impedance matching device. Assume that the output impedance of the radio is 50ohm (this can really be any value), and that the input impedance to free space (air / atmosphere / whatever you want to call it) is about 377ohm (see en.wikipedia.org/.../Impedance_of_free_space). It's a matching device, and should not be considered a stripline. Discussions about the length of the antenna, "shape" of the antenna, etc are for another day.

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