Mutual Coupling Reduction Between Two Tightly Packed Half-Split Cylindrical Dielectric Resonator Antennas

An efficient and advanced decoupling technique is presented to significantly reduce the mutual coupling in the ${E}$ -plane between two tightly spaced half-split cylindrical dielectric resonator antennas (CDRAs). The proposed design offers around 59% reduction in the overall electrical footprint compared to the reference two-port full CDRA antenna exhibiting the same mutual coupling performance. This is possible by the vertical placement of copper-cladded FR-4 substrate with air gaps between two halves and maintains the boundary condition to support the dominant $\mathrm {\textbf {HEM}}_{\textbf {11}\boldsymbol {\delta }}$ mode of CDRA. A significant reduction in mutual coupling is obtained precisely at the antenna resonance by controlling the dimensions of the decoupling structure, leading to its minimum value. The proposed technique appears flexible and provides a comprehensive design guideline to tune the return loss and mutual coupling minima. A detailed analysis is performed with an equivalent circuit model to explain the decoupling mechanism and its precise control for optimal performance. Measured S-parameters show a −10-dB impedance matching bandwidth of 16% (4.54–5.34 GHz) and −44 dB mutual coupling at 4.9 GHz, reaching −62.3 dB at 4.86 GHz. Within the operating bandwidth, the measured gain lies between 4.6 and 6 dBi, and the envelope correlation coefficient is below 0.053. The results indicate that the two-port antenna is a good candidate for multiple-input multiple-output (MIMO) communication.