An Idea to Reduce the Mutual Coupling in Rectangular Dielectric Resonator Antenna for MIMO Applications

This paper presents a two-port highly isolated antenna comprising of two half-split rectangular dielectric resonator antennas (RDRAs). For the isolation enhancement, a both side copper-cladded FR-4 substrate with air gaps is placed between the half-split RDRAs. The copper cladding of the FR-4 substrate acts as a perfect electric conductor and thus maintains the boundary condition to excite the $\mathrm{T}\mathrm{E}_{\delta 11}$ mode. By varying the thickness of the FR-4 substrate, the mutual impedance between antennas can be brought down to its minimum value, which ultimately leads to low mutual coupling between them. The -10dB reflection bandwidth for this 2-port antenna is from 6 to 6.765 GHz (10.5%). For a very small inter-element spacing of $0.054\lambda_{0}$, the mutual coupling is found below -27.5dB over the entire operating bandwidth with the lowest value of -62.3dB. Antenna gain is noted to be lying between 6.03 and 6.64 dBi. The envelope correlation coefficient (ECC) is maintained below 0.0294 across the bandwidth. Therefore, this antenna can be used for 2-port MIMO applications.