In this paper, a simple novel technique to self-isolate multiple-input-multiple-output (MIMO) antenna array elements for mm-wave applications is proposed. MIMO antenna arrays with inter-element separation of 0.2 mm (0.023λ at 35 GHz) and measured high isolation (>50 dB) are presented. Several rigorously optimized slots of different shapes, positions, and dimensions are etched on the radiating patch to enhance the inter-element isolation within 28-37.5 GHz impedance bandwidth.
The surface current distributions, parametric analysis, and two MIMO array configurations are employed to validate the proposed self-isolation technique. The novel mm-wave antenna exhibits high impedance bandwidth (>29%), high isolation (>50dB), high efficiency (>90%), high gain (>9.5 dB), and low envelope correlation coefficient (<0.005) throughout the desired bandwidth.
Two configurations of the MIMO antenna arrays are fabricated and measured to validate the simulation outcomes. To the best of the authors’ knowledge, the presented design is the first to exhibit such wideband isolation improvement without any external decoupling structure at the mm-wave frequency range.