Superdirective antenna with artificial dielectric substrate

A superposition of spherical orthogonal modes allows to achieve in theory, radiation directivity as high as desired. However, spherical modes lead to impractical feeding elements. A simpler case of mode combination is introduced here which uses only azimuth variations and is fed by annular rings. The size of the ring radiators representing given modes is reduced by the application of artificial dielectric. This technique provides more freedom in realization of (azimuth) modes, allows to reduce the size of the system without reducing the directivity, and can produce superdirective antenna.