A multiband ringed rectangular patch antenna

This paper presents a multiband, electrically small patch antenna with dimensions 147.9 mm by 90.4 mm and an inset microstrip feed. The length of this antenna is suited to a 0.5 GHz resonance. The geometry of the patch has been modified from its traditional form by introduction of five 0.6 mm gaps just inside its outer edge. The effect of these gaps is to reduce the highest frequency of resonance from 500 MHz to 446 MHz, and to introduce three additional resonances, at 353 MHz, 389.5 MHz, and 412.5 MHz.