A Compact Dual-Decoupling Scheme for Aperture-Coupled and Probe-fed Closely-Spaced Wideband Microstrip Antennas

In this paper, a compact wideband dual-decoupling technique is proposed for wideband microstrip patch antennas (WMPAs) at the X band. The wideband decoupling property is achieved by integrating the defected ground structure (DGS) and the coplanar inductance on the ground plane and patch layer, respectively. To validate the feasibility of the proposed method, both the aperture-coupled and probe-fed WMPAs with the proposed novel decoupling scheme are simulated, fabricated, and measured, respectively. An equivalent circuit and characteristic mode analysis (CMA) of this wideband decoupling scheme are developed to provide physical insight succinctly. Experimental results demonstrate that the poor isolation of the two proposed antennas has been improved from 6 dB to better than 20 dB with an extremely close edge-to-edge distance of 1 mm (0.033 λ 0 ). The achieved decoupled bandwidths are up to 17.6% and 22.2 % for the aperture-coupled and probe-fed schemes, respectively. In addition, the proposed method has also been extended to the decoupling of multi-element antenna arrays, demonstrating its potential for large-scale wideband massive multiple-input and multiple-out (MIMO) applications.