Miniaturization of Patch Antennas Using a Metamaterial-Inspired Technique

A new design methodology for producing highly miniaturized patch antennas is introduced. The methodology uses complementary split-ring resonators placed horizontally between the patch and the ground plane. By optimizing the geometry of the split rings, sub-wavelength resonance of the patch antenna can be achieved with a good impedance match and radiation characteristics comparable to those of a traditional patch antenna on a finite ground plane. Construction of the optimized antenna is straightforward, requiring only the sandwiching of two etched circuit boards. High levels of miniaturization are demonstrated through simulations and experiments, with reductions of a factor of more than four in transverse dimension achieved for a circular patch resonant at 2.45 GHz. Although miniaturization is accompanied by a decrease in antenna radiation efficiency and a loss of fractional bandwidth, antenna performance remains acceptable even for a 1/16 reduction in patch area.