A metamaterial-based compact multiple-input multiple-output antenna with pattern diversity

A compact multiple-input multiple-output (MIMO) antenna is proposed with dual-mode pattern diversity. A two-port antenna with a single radiator is designed based on the composite right/left-handed transmission-line (CRLH-TL) theory. An omnidirectional radiation pattern is excited by the port 1, while a directional radiation pattern is excited by the port 2. When the omnidirectional radiation pattern is excited, the antenna can be regarded as a radial CRLH-TL-based resonator. When the directional radiation pattern is obtained, the antenna is modeled as a circular patch antenna. The two different radiation patterns are integrated in one antenna with low complexity and low cost. The electrical size of the proposed antenna is 0.6 × 0.6λ² (at 3 GHz). A low profile of only 0.07λ is obtained. The antenna works at the 3 GHz band. The measured −10 dB bands for port 1 and port 2 are 2.71–3.06 GHz and 2.87–2.96 GHz, respectively. A low mutual coupling below −30 dB between the two radiators is achieved, which decrease the channel correlation significantly.