An RF beam steering device according to present invention embodiments employs a prism assembly to steer an RF beam. The prism assembly includes a plurality of dielectric prisms each with an associated impedance matching layer. The dielectric prisms are rotated relative to each other to steer the RF beam. The prisms include a plurality of individual panels with drilled or slotted openings that are arranged to create a periodic photonic crystal structure within a defined region. This configuration effectively alters the dielectric constant over any one particular region of a panel, thereby altering the level of diffraction possible for a specified panel thickness. The openings within each stacked panel are overlapped to produce the required level of diffraction and refractive index gradient. Motors rotate the prisms relative to each other to the correct orientation for steering the RF beam in a desired manner.