Micro-Magnetic Radiators for RFID Tags

The paper discusses the design and realization of micro-magnetic antennas, as an optimal solution to manufacture RFID tags embedded in dissipative materials. Magnetic antennas are preferable for any application involving the insertion of the radiator in a lossy medium. A micro design is introduced, which allows the realization of a small magnetic dipole that exhibits an excellent omnidirectional radiation diagram. Moreover, thanks to a compact design and a small size, the proposed antennas can be embedded in a narrow space, with extremely limited spatial dimension. On the contrary, small antennas have limited radiating characteristics, with a light efficiency and a high mismatch. The described approach reduces the overall antenna dimensions by selecting an efficient geometrical shape and embedding the matching circuit inside the antenna. The return loss has a 0.6% bandwidth at -10 dB, larger in comparison to other realizations than can be found in the literature. Although several realizations s have been carried out, two solutions working 900 MHz with simulations and measurements is presented. For their shape, they have been baptized, respectively, Smiley and Hair Antennas.