A Compact Radiation-Pattern-Decoupled MIMO Antenna With Different Radiation Directions

This article presents a compact multiple-input multiple-output (MIMO) antenna featuring radiation pattern decoupling (RPD) characteristics in various radiation directions for the first time. The well-designed multifunctional dielectric decoupler (DD) can modify the spatial coupling between patch antennas (PAs) and between endfire antennas (EAs). The top layer of the DD, as well as the metal structures (director and radiator) combined with the DD, enabled the PA and EA elements to obtain RPD characteristics based on the coupling field and current superposition cancellation. The interleaved configuration of PA and EA elements makes the MIMO antenna more compact and significantly improves antenna space utilization. An MIMO antenna prototype with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1\times 3$ </tex-math></inline-formula> PAs and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1\times 4$ </tex-math></inline-formula> EAs is designed, fabricated, and measured for the 5.8-GHz band. The measured results are in good agreement with the corresponding simulated ones. The overlapping −10-dB impedance bandwidth of antenna elements is 3.6% (5.75–5.96 GHz), over which the isolations between any antenna ports are higher than 16.5 dB. It is worth noting that the presented compact MIMO antenna radiates in two different directions and exhibits RPD characteristics, which make it a valuable design for different application scenarios.