Fig. 15 shows the comparison of S-Parameter graph when the antenna is in free space and mounted on an aluminum plate with the dimension of 40 x 40 cm2. From the graph it can be seen that the resonant frequency only slightly shifted to the higher frequency when the tag is attached on metal object and the reflected power of the tag antenna is below than 10% in both conditions. This result proved that this tag can be used on metal object.
Frequency