Implementation of Broadband Isolator Using Metamaterial-Inspired Resonators and a T-Shaped Branch for MIMO Antennas

We develop a novel MIMO antenna with excellent broadband isolation performance in this communication. Metamaterial (MTM)-inspired resonators can function as insulators and are placed periodically into a compact MIMO antenna system for portable applications. These insulators only need a 0.18 wavelength. The broadband insulators can efficiently reduce the coupling of MIMO antennas. Isolation bandwidth under 20 dB can reach 8% with relative to the center frequency. Adding a T-shaped branch behind the insulators markedly improves the isolation bandwidth. An isolation bandwidth under 20 dB can achieve 19.3% relative to the center frequency. The effectiveness of the proposed insulators is validated by measurements.