Low-Profile Dual-Band Pattern Diversity Patch Antenna Based on Composite Right/Left-Handed Transmission Line

A low-profile patch antenna with pattern diversity is proposed. The topology combines an annular ring together with a center-fed circular patch. The composite right/left-handed transmission line is loaded on both the annular ring and the circular patch, to realize the 2.4/3.5-GHz dual-band operation. The outer annular ring works at its first pair of symmetric modes, which results in broadside radiation patterns, while the inner circular patch provides omnidirectional patterns in the horizontal plane, as a consequence of its physical circular symmetry. The field distribution is analyzed to verify the operational principle. By optimizing the feeding network, the antenna reaches a good impedance matching in both bands. A prototype is fabricated, and the measured results agree well with the simulated ones. The measured correlation coefficient is lower than 0.04 and 0.05 in the lower and upper band, respectively.