This work introduces a new design approach of multilayer Electromagnetic Band Gaps (EBGs) for wideband antenna isolation in a Full-Duplex transceiver. The design methodology is applied to a conventional type of EBGs in order to improve its initial performance in terms of bandwidth and size. By stacking multiple dielectric layers with integrated vias, an enhancement of the relative bandwidth of the band gap and a strong miniaturization of the unit cell is achieved. The dispersion diagrams of the proposed EBGs are studied and full-wave electromagnetic simulations are realized to validate the isolation level and the proposed lumped model of the final structures.