Basic NFC Loop Design on PCB
You don't need to match the output from the coil to 50 ohms if you are using 13.56MHz BUT, you do need to have a load on the receive power coil that is representative of the power you might be wanting to extract when powering a passive NFC device.

At 13.56 MHz, the dominant field is magnetic i.e. it is an alternating magnetic field that transfers all the power from coil A to coil B and as such you need to make life easier by resonating the coils as tuned circuits. This is done by series or parallel capacitors added to each coil.

However, the basic idea for transferring power is embodied in the following: -



From this you should be able to realize that the two coils can be identical or different size (identical is probably the easiest to get power through however). Because either coil is working as a magnetic loop antenna, either termination can be your 0V reference. Earth (ground) as a concept is unimportant for this type of antenna.