This configuration offers spacing of 4 to 15 mm of space between the tags and the metallic cans.
Attention was not put towards precise tag positioning; therefore, some tags may have been closer to metal than others.
The only missed tag was situated at the bottom of the fourth row of pallets (Fig. 3a).
This particular tag may have been precisely sandwiched between two cans (too close to metal), or the RF wave scattering pattern may have created a null area where the energy was not high enough to allow tag response.