Compact microstrip patch antennas for passive RFID backscatter tags

Passive radio frequency identification utilizing the scattering from electrically small resonators is a known principle. In this work the advantages of using compact microstrip patch antennas for small resonant tag inclusions are investigated. It is demonstrated that these antennas exhibit superior scatter performance compared to dipole like antennas when placed on conducting or high dielectric surfaces or in view of polarization dependence. Additionally they can be designed to scatter orthogonally polarized waves related to the incident wave. This property promises improved signal quality if the tag is mounted on an object with high reflective properties.