A Compact MIMO Antenna using ZOR Split Ring Resonator Radiators with a Decoupling Structure

This article presents a novel compact MIMO antenna for mobile communication devices, which has miniaturized antennas with increased isolation and operates in the WiMAX and LTE high bands. Each of the proposed element antennas is designed to have the in-phase electric field distributions of the zeroth order resonance (ZOR) in the form of a CRLH type split ring resonator (SRR), which is much smaller than the conventional SRRs and other antennas for MIMO communications. These antennas can be placed in close vicinity, using a small planar mushroom decoupling structure between them, in order to meet the required isolation level. The design is carried out by full-wave electromagnetic simulations, which prove the ZOR characteristic of the antennas and the suppressed interference from one antenna to the other This proposed MIMO antenna was fabricated and measured to show a return loss better than 10 dB, an isolation greater than 12 dB and a radiation efficiency over 50 percent in the WiMAX and LTE high bands for both antennas. The total size is 26 x 5.5 x 2 mm, which fits within half of the top-edge of the ground of handset phones.