An electronic device includes a first layer with an antenna and a second metal layer that extends over the entire first layer. The second metal layer includes at least one laterally-closed cavity that is located vertically above the antenna. The cavity is filled, at least in part, by a resin material. A first plate supporting a second metal plate extends over the cavity with the second metal plate positioned vertically above the antenna. The first metal plate may be supported by a ledge within the cavity. Alternatively, the second metal plate is embedded in the resin filling the cavity, with the second metal plate positioned vertically above the antenna.