||Image of the Circular tapered polyrod with horn-launcher.
Dielectric-rod antennas, also known as Polyrod antennas, are regarded as a type of surface-wave antenna. While a wide range of configurations are possible for dielectric-rod antennas, in most cases they have a tapered rod of circular or rectangular cross section. In these antennas, the feeding waveguide couples part of the input power into a surface wave which travels along the dielectric rod with minimal reflection. The surface wave then continuously radiates as it travels along, gradually transforming from a strongly bounded wave to a free-space wave.
Reduced side lobe levels are attainable through proper design, however this also results in reduced gain. By adding a horn launcher (or a short flared section at the waveguide termination) a further reduction of the side lobe level may be achieved....