An electronic device case includes a conductive cap section and a conductive bezel section forming a perimeter outside the conductive cap section and separated from the conductive cap section by a bezel gap. A conductive ground plane section forms a perimeter and is positioned opposite the conductive cap section and the conductive bezel section. The conductive ground plane section is separated from the conductive bezel section by a perimeter gap. One or more components reside between the conductive cap section and the conductive ground plane section forming a resonant cavity including a ground plane resonant cavity portion between the one or more components and the conductive ground plane section and a substantially annular resonant cavity portion between the one or more components and the perimeters of the conductive bezel section and the conductive ground plane section.