Compact Microstrip Antenna for RFID Application
Asymmetric-circular shaped slotted microstrip patch antennas with slits are proposed for Circularly Polarized (CP) radiation and radio frequency identification reader applications. A single-feed configuration based asymmetric-circular shaped slotted square microstrip patches are adopted to realize the compact circularly polarized microstrip antenna. The CP radiation can be achieved by slightly asymmetric patch along the diagonal directions by slot areas. Four symmetric-slits are also embedded symmetrically along the orthogonal directions of the asymmetric-circular shaped slotted patch to further reduce antenna size. The operating frequency of the antenna can be tuned by varying the slit length while keeping the CP radiation unchanged.