An apparatus includes a first layer having an RF lossy material, a second layer having the RF lossy material, and a plurality of conductive or resistive pads arranged in a planar array between the first layer and the second layer. The apparatus may also include a plurality of thermal vias, where each thermal via may correspond to one of the pads, may extend through at least the first layer, and may be formed of a thermally-conductive material. Dimensions of each pad may be selected based on a desired resonant frequency band, and the desired resonant frequency band may be associated with RF energy transmitted by at least one RF source in proximity to the apparatus.