I have only the MFRC522 I.C. with the default design as shown in the datasheet of the I.C. on page 81 but from my ANTENNA knowledge I know if you inject more current in the system I may extend the effective range to more than 50mm but I am not sure how to do this plus If I use active card I can achieve this but how since the I.C. is very sensitive with low power mode (very preferable) I do not want to damage the I.C. ??? where a max. range is very preferable (in the order of 100mm or more)
P.S. I have this circuit made by a Chinese manufacturer and marketed as ARDUINO equipment!