The final structure and dimensions of the proposed
compact circularly polarized RFID tag antenna is shown in
Fig. 1. The antenna is fabricated on a FR4 substrate
( 4.4 ε r = , tan 0.02 δ = ) with a dimension of 68 68 mm mm ×
and thickness of H ( H mm = 1 ). Two pairs of slots with
unequal lengths 1 S , 2 S and equal width t ( t mm = 1 ) are
embed into the crossed dipole, respectively. The crossed
dipole is folded for a size reduction. A modified inductivelycoupled-fed
small loop with length and width is applied,
and an IC chip is attached to the middle of one side of the
loop, which is the green area as shown in Fig. 1.