Surface matching of dielectric lenses

Two methods of cancelling the surface reflections of dielectric lenses are described. The first utilizes a simulated quarter-wave matching layer, and the second a reactive wall embedded within the dielectric. The reactive wall may take a variety of physical forms, such as arrays of thin conducting discs, which have a capacitive reactance, or arrays of thin wires, which have an inductive reactance. Surface matching is obtained when the discs are placed approximately 3/8 wavelength inside the lens, or the wires 1/8 wave-length Curves are presented that show how the reflections at the air and dielectric boundary are reduced for various angles of incidence and polarization when quarter-wave layer and reactive-wall matching are employed. The reactance of the array of discs for waves incident at various angles and polarizations is computed by means of Bethe´s small aperture theory, and Babinet´s principle. Measurements in waveguide of the reactance of an array of circular discs for various angles of incidence and for both E- and H-plane polarization show close agreement with the theory.