Design of fragment-type isolation structures for MIMO antennas

Fragment structure should flnd its application in acquiring high isolation between multiple- input multiple-output (MIMO) antennas. By gridding a design space into fragment cells, a fragment- type isolation structure can be constructed by metalizing some of the fragment cells. For MIMO isolation design, cells to be metalized can be selected by optimization searching scheme with objectives such as isolation, return losses, and even radiation patterns of MIMO antennas. Due to the ∞exibility of fragment-type isolation structure, fragment-type structure has potentials to yield isolation higher than canonical isolation structures. In this paper, multi-objective evolutionary algorithm based on decomposition combined with genetic operators (MOEA/D-GO) is applied to design fragment-type isolation structures for MIMO patch antennas and MIMO PIFAs. It is demonstrated that isolation can be improved to difierent extents by using fragment-type isolation design. Some technique aspects related to the fragment-type isolation design, such as efiects of fragment cell size, design space, density of metal cells, and e-ciency consideration, are further discussed.