In this paper, a novel zeroth-order resonator (ZOR) antenna by exciting two asymmetric coplanar strips (ACS) is reported. In order to attain ZOR resonance, the antenna has resorted to two annular ring resonators (ARRs) which control antenna characteristics at 2.7 GHz. In this frequency, antenna treats such as a planar dipole antenna with omnidirectional patterns and linear polarization. The proposed antenna by utilizing two ports can change circular polarization diversity at the second band region. The proposed miniaturized antenna covering more than 80% bandwidth overall two bands and a more than -15 dB isolation between two input ports can be used in portable systems.
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