A multiple antenna assembly with high isolation between the antennas is disclosed. The assembly includes a dielectric substrate with a ground plane and first and second antennas thereon. One or more metal-dielectric isolation structures are on the substrate at locations at which an electric current is present that has a current density greater than a predefined threshold. Each metal-dielectric isolation structure resonates at a given frequency that inhibits mutual signal coupling between the first and second antennas. Various configurations, such as concentric ring patterns, for the metal-dielectric isolation structures are disclosed. A device can be provided to dynamically tune the given frequency of the metal-dielectric isolation structures to correspond to radio frequency signals emitted by the first and second antennas.