Miniaturised slit-patch EBG structures for decoupling PIFAs on handheld devices

Double-layer miniaturised structures are presented for reducing the mutual coupling between closely spaced PIFAs on a handheld device ground plane. The proposed structures employ two closely coupled layers, one made of conducting linear patches and another made of apertures (slits) in a ground plane. They are placed in very close proximity to each other (55μm) with a rotation of 90° between the elements in order to produce maximum coupling. The dimensions of the proposed structures are optimised to produce maximum miniaturisation thereby occupying very little space on a compact ground plane. A microstrip line excitation is initially used for the efficient analysis and design of the structures. Two PIFAs are subsequently used and the mutual coupling reduction is demonstrated. Results obtained in 3D electromagnetic simulation software (CST Microwave studio) are presented.