Antenna array element decoupling by means of electromagnetic bandgap (EBG) structures is investigated. A dielectric cover layer is proposed to reduce the EBG lattice size. Its influence on a classical mushroom EBG structure is analyzed in detail. It is shown to decrease the bandgap center frequency by up to 32% for a given structure size. The successful implementation in a generic array with half wavelength element spacing at K-band is demonstrated.
