An electromagnetic device includes: a first layer having a first material with a first dielectric constant, the first layer having a plurality of channels or holes filled with a second material with a second dielectric constant that is different from the first dielectric constant; and, a second layer having a plurality of antennas disposed on the first layer. Adjacent ones of the plurality of channels of the first layer have an average spacing therebetween of less than one quarter of an operating wavelength of at least one of the plurality of antennas.