Radiation from slots in artificially soft and hard cylinders

The radiation fields of circumferential slots in soft and hard cylinders are calculated for the case in which the slots are excited by a TE₁₁ circular waveguide mode. The results are compared to those for a smooth conducting cylinder, showing that the soft surface strongly reduces the intensity of the field radiated along the cylinder whereas the hard surface enhances it. The results are applicable to the design of self-supported feeds for paraboloids, and to the analysis of the line feeds of the radio telescope at the Arecibo observatory. The calculations are confirmed by measurements