Single-feed circularly polarized square-ring microstrip antennas with a slit

By inlaying a narrow slit at the edge of a square-ring microstrip antenna, both the compactness and circular polarization (CP) operation can be easily achieved. Typical designs have been implemented. From the experimental results obtained, the required antenna size using the proposed design method can be reduced by about 19% of that of the conventional design method using a nearly square patch for CP operation without a slit.