Millimeter-Wave Magneto-Electric Dipole Isolation Enhancement using Superstrate-Based Decoupler

This work presents a superstrate-based decoupler to increase the isolation between two closely spaced Magneto-Electric (ME) dipoles in the 52–64 GHz millimeter wave (MMW) frequency band. The decoupler consists of a single row of 15 vias, and a copper plate carefully inserted into a high-permittivity superstrate between the two-element MIMO antenna. The vias help to mitigate the surface coupled waves in the antenna substrate, while the copper plate and the high-permittivity superstrate help to alter the space permittivity, disturb the space coupling, and increase the isolation. This combination improved the proposed antenna's isolation by a maximum of 31 dB over the 52–64 GHz bandwidth (14.3%) in the H-Plane, with a very close edge-to-edge spacing of 0.62 mm (0.12λ), where λ is the free-space wavelength at the center frequency of 60 GHz. Additionally, the superstrate-based decoupler structure improved the antenna's bandwidth (52–70 GHz), without distorting the radiation pattern.