OK, now I know what I did not know a few days ago. I could not stop thinking about the Clickboard with only 100 pF capacitor as a matching circuit. Now, I know more and I am going to describe it to you here. How do I know? I found a comprehensive Application Note AN11276 NTAG Antenna Design Guide by NXP.
The used antenna of the Clickbord or similar Class IV antenna:
👍54x27 mm, 0,3 mm track width, 0,9 mm turn gap
1️⃣input capacitance of the chip is 50 pF
2️⃣capacitance of the antenna is about 1,4 pF - based on a calculation done by AntennaTool
3️⃣Inductance of the antenna 913 nH
Once you add 100pF capacitor to the complete capacitance C = 50 + 1,4 + 100 pF = 151,4 pF and calculate resonant frequency of the LC tank, you get...voilá.... 13,54 MHz
My antenna will be a little different:
👍60x60 mm, 0,25 mm track width, 0,25 mm turn gap
1️⃣input capacitance of the chip is 50 pF
2️⃣capacitance of the antenna is about 2,4 pF - based on a calculation done by AntennaTool
3️⃣Inductance of the antenna 1644 nH
I have to add capacitance of Cmatch = 31,6 pF to get the resonant frequency of 13,54 MHz.