Dual-Band Circularly Polarized Patch Antenna With First Positive and Negative Modes

A dual-band circularly polarized (CP) patch antenna having a first positive ( +1) mode and negative ( -1) mode is proposed in this letter. The +1 mode is a half-wavelength mode in the right-handed (RH) region, and the -1 mode is induced by a composite right/left-handed (CRLH) transmission line (TL) in the left-handed (LH) region. In order to realize CP properties, a trimmed square patch antenna and a 2 × 2 triangle mushroom antenna are employed, respectively, and the two antennas are combined to obtain small size. The proposed antenna has a single feed and a single-layered substrate even though it contains two antennas. Measurements show that the antenna has CP bandwidths of 2.879-2.901 GHz at the low band and 3.822-3.829 GHz at the high band. Finally, peak gains of 6.26 and 6.97 dBic are obtained and radiation efficiencies of 82% and 65% are measured at each band, respectively.