B. Antenna Gain and Radiation Pattern Fig.16 shows the radiation pattern of the proposed tag antenna in free air and on metal object at 921 MHz. The radiation pattern of the tag antenna becomes more directional when the tag is attached on metal object. The realized gain of the tag attached on metal object is slightly higher than the tag in free air as shown in Fig. 17. Fig. 18 shows the current distribution on the surface of the tag antenna. It can be seen that the current is extremely high at the meander feed line and distributed equally at the rectangular loop of the tag antenna.