Backfire antennas aim at direct broadcast TV

The basic backfire antenna is essentially a cavity-resonator component, with electromagnetic characteristics comparable to those of a laser cavity. There are two varieties: short and long, depending on the surface-wave structure linking the reflectors. Performance parameters are discussed for both modes, noting that waveguide feed is better than a dipole structure for short backfire antennas, and that the high gain realized by the slow-wave structure in long backfire antennas makes it comparable in performance to the much larger horn antennas. High gain coupled with compact size make backfire antennas well suited for direct broadcast satellite systems at 12 GHz.