Modelling the Effects of Stacked Paper on the Radiation Pattern of Bow-Tie RFID Tag Antennas

In this paper a bow-tie antenna in air and between paper reams with different parameters has been studied. Antennas in two different paper dielectric constants were simulated. The resonance frequency lowers about 250 MHz more with paper epsi_r=4 than epsi _r=2, and with the smaller antenna. The return loss disimproved about 5 dB in almost all cases. These results indicate that the electrical dimensions have to be tuned to achieve the desired resonance frequency and impedance matching inside the paper layer. Paper increases the directivity in all cases. The effects on radiation pattern were more radical with paper epsi_r=4 than epsi_r=2 and with the bigger antenna size. Adding paper reams on antenna increases the main lobe in the direction where the paper is added. In the future, a simulation model for a paper reel, where the paper is wrapped around the reel core and the tag antenna can be developed