Reduction of Patch Antenna Coupling by Using a Compact EBG Formed by Shorted Strips With Interlocked Branch-Stubs

This letter presents a new type of planar electromagnetic band-gap (EBG) surface composed of short-circuited microstrips densely coupled with each other through interlocked branch stubs. With respect to a conventional mushroom surface, this structure exhibits a better space-wave decoupling performance due to the "soft" nature of the surface. With respect to other soft surfaces, like shorted strip already introduced in the literature, the present solution possesses better miniaturization properties, thus allowing the use of lower permittivity and consequent improvements when integrated in planar dense arrays. The experimental results demonstrate a decoupling until 38 dB in both planes for patches separated by only one half free-space wavelength.