Null mitigation of planar RFID tag antennas

Printed monopole and dipole antennas for RFID tags have inherent nulls in their radiation patterns. These nulls in radiation patterns limit tag reading even if a circularly polarized reader antenna is used. The paper presents ten various conventional and novel printed antennas to improve the nulls for maximum visibility of the tag. The investigation reveals that highest null improvement of 25 dB in monopole and 24.6 dB in dipole is possible using non-conventional monopole and dipole.