A Three-Port MIMO Dielectric Resonator Antenna Using Decoupled Modes

In this letter, we propose a three-port multiple-input–multiple-output (MIMO) dielectric resonator antenna using three mutually decoupled and near-degenerate modes for <italic>X</italic>-band applications. To achieve decoupling, two of the three excited modes are chosen such that there is low mutual spatial overlapping between their field magnitudes; then, a third mode is imposed such that its field components are perpendicular to the other two modes. The impedance bandwidths of the three ports are 880 MHz, 870 MHz, and 2.61 GHZ, respectively, where contiguous bandwidth for the third port is achieved by utilizing the overlap of two resonances of <inline-formula><tex-math notation="LaTeX">$TE_{2 \delta 1}^{y}$</tex-math></inline-formula> mode. The proposed antenna could be used either as a three-port MIMO antenna with operating bandwidth of 720 MHz, or as a two-port MIMO antenna with operating bandwidth of 880 MHz, at center frequency of 9.48 GHz. The gains of the three patterns at center frequency are 8.1 dB, 7.5 dB, and 7.4 dB, respectively.