A Compact Square Circular and Cross Shaped Slotted Patch Antenna for RFID Application

A compact cross, circular and square shaped slotted microstrip patch antennas are designed for circularly polarized (CP) radiation. The designed antenna is fabricated on RO4003C substrate and measured using Agilent network analyzer. The simulated return loss of this proposed antenna is less than -16dB at 920MHz with a bandwidth of 3MHz which is most suitable for RFID application. The circular polarization radiation pattern and axial ratio parameters are compared for square, circular and cross shaped antennas. The simulated gain is more than 3dBi for all three antennas. A symmetric, cross shaped slot is embedded along one of the diagonal axes of the square patch for CP radiation and antenna size reduction. The overall size of the antenna with CP radiation can be reduced by increasing the perimeter of the symmetric cross-shaped slot within the first patch quadrant of the square patch. The return losses of the measured results are in agreement with simulated results, the measured S parameters and radiation pattern showed that the proposed design is suitable for RFID frequency regions.