Bandwidth enhancement technique for quarter-wave patch antennas

A novel technique that improves the performance of a conventional quarter-wave patch antenna is proposed. Two different geometries (U-slot and L-slit) are investigated experimentally. With the inclusion of a folded inner small patch, we achieve impedance bandwidths of 53% and 45% for the U-slot and L-slit, respectively, for a voltage standing wave ratio less than 2. Radiation patterns are stable across the whole operating frequency bands.