Meander coil shape for RFID/air transformer
A meander structure (it's not a "coil") is very inefficient for creating a magnetic field by electric currents because adjacent currents go in opposite directions, i.e. magnetic fields cancel out.

It's much more effient to use a real coil structure (e.g. spiral), i.e. adjacent currents will go in the same direction, i.e. magnetic fields add up.