Considerations on the use of commercial loop modules in the excitation of UHF RFID antennas

The purpose of this paper is to clarify the principles, advantages and disadvantages of commercial RFID modules combining a loop and a RFID IC for the excitation of dipole-like antennas. Using a circuit modeling of the tag topology, the influence of the main parameters (dipole radiation resistance and Q factor, module position along the dipole, mutual coupling between the loop module and the dipole) are stressed. A special attention is brought to the determination of the optimal coupling for a given dipole.