Design of a Tag Antenna for RFID Applications

This paper introduces a meander line printed dipole antenna with a miniaturized size for RFID at 915MHz applications. A fractal geometry based on a third-order Hilbert structure is introduced as a matching circuit to overcome the impedance-matching limitations of printed meander antennas. Next, the proposed meander structure is introduced to increase the electrical length within a limited substrate size. Such technology supports size reduction. However, the induction current's effects are augmented due to the meander turns. Therefore, introducing the Hilbert fractal curve realizes a capacitive effect, significantly reducing the induction effects. For this, the radiation losses due to the inductive part are canceled ultimately by the capacitive parts induced by the fractal structure. This acquires to keep the resonance frequency at 915MHz with maximum radiation efficiency to get a realized gain of 1.46dBi with a radiation efficiency of 90%. A parametric study supports the design methodology to monitor the effects of varying the antenna dimensions on S11 and Z11 spectrums. The antenna radiation pattern at the desired frequency band (915Mhz) is presented in 3D to observe an omnidirectional pattern. Finally, it is found that the proposed antenna is very suitable for the applications of RFID systems within a moderate communication distance of 5.07 m.