Hello @Rohit ,
The distance of communication between reader and tag is fixed as per the NFC standards. The NFC communication occurs at the fixed frequency of 13.56 Mhz and the principle behind the NFC operation is Inductive coupling. As mentioned by Jayden the proper placement and the orientation of the Antenna will help you to get the best result.
Please make sure that the size of the receiver antenna should match the size of the transmitter antenna for the good coupling. Please refer to the Antenna design guide which will help you to select the proper antenna for your application. It's not like increasing the antenna size will improve communication stability but the most crucial factor is proper antenna coupling. By changing the output power may help probably to increase the distance but without good coupling between two antennas it will not help much.
For more details refer to the product page of NAC1080.
Regards,
Kanahaiya
