Practical realization of superdirective arrays

Developments in experimental active and passive superdirective antennas are reviewed. Particular attention is given to the author´s work on a two wavelength passive array consisting of nine open-ended waveguide radiators spaced one quarter-wavelength apart. The broadside superdirective patterns for this array are shown and the unnecessary restrictions on the bandwidth, due to the feeding system and the measuring site, are discussed. A new family of superdirective patterns is reported and it is shown that the far-field of a superdirective antenna starts at a distance which is no further from the antenna than that for the equivalent non-superdirective antenna. It is also shown that the high reactive field associated with superdirective arrays is confined to the immediate vicinity of the antenna.