AN5276: error in the correction factor in section 4.3 Antenna equivalent circuit?

[navii]

the document said, the correction factor is due to skin effect, but the K formula seems make a mistake (inverted). should it be Rp@fwork/Rp@fres = K = √(fwork/fres) instead, so the value is incorrect too?(as for skin effect, with frequency increase, the R should increase) 

[ms_vahle · Accepted solution]

I think an increase in resistance due to the skin effect for increasing frequencies would reduce the quality factor of the coil. As the coil is modelled as a parallel resonant circuit in the application note, the quality factor drops for smaller resistance values, as Q = R / (w*L). For the NFC case, the self resonant frequency is typ. larger than the 13.56MHz operating frequency. Hence, skin effect should be smaller, quality factor should rise and hence also the parallel resistance in the equivalent circuit should rise.