A Multistandard Antenna Based on a 2-D CRLH-TL in Polar Coordinates

A novel 2-D composite right/left-handed transmission line (CRLH-TL) metamaterial in polar coordinates is proposed for the first time, and applied to a multistandard antenna. The prototype antenna with triband operation and colocated pattern and polarization diversity is specifically designed to eliminate the need for multiple antennas in the processing center side and to significantly reduce antenna area and cost. Radial CRLH-TL waves of mode type 0 and 1 are simultaneously excited by port 1, working in the 2.5 GHz Industrial, Scientific, and Medical (ISM) band and the 3.3 GHz WiMAX band, respectively. Annular CRLH-TL waves of mode type -1 and +1 are simultaneously excited by port 2, covering the 915 MHz RFID band, and the 2.5 GHz ISM band, respectively. The 0 and 1 modes in the r-direction result in omnidirectional patterns due to the circular symmetry. The -1 mode and +1 mode in the φ-direction result in directional patterns, thanks to the aperture-coupled feeding topology.